*This tutorial demonstrates various ways of entering dates in Excel. See how to insert today's date and current time as static time stamp or dynamic values, how to auto populate a column or row with weekdays, and how to auto fill random dates in Excel.*

There are several ways to add dates in Excel depending on what exactly you want to do. For example, do you want to enter a today's date in some report or invoice? Or, perhaps you want to insert a date in Excel that will update automatically and always display the current date and time? Or, maybe you want to auto fill weekdays or input random dates in your worksheet?

In a moment, you will learn all these and a few more date entering techniques. If you are curious to know how Excel stores dates and times, please check out part 1 of this tutorial - Excel date format.

### How to enter a date in Excel

You can type a date in an Excel cell in a variety of ways, for example 1/1/2015, or 1-Jan-2015, or 1-Jan, or January 1, 2015. When you type something like that in a cell, Microsoft Excel knows you are entering a date and automatically applies the date format to that cell. Quite often, Excel formats the newly inserted date according to your Windows default date settings, but sometimes it may leave it exactly as you typed.

The most obvious visual indication that Excel has recognized the date you've entered is its right-alignment in a cell as opposed to left-aligned text values.

If Excel has failed to recognize your input as a date and you see it left-justified in a cell, try inserting a date in some other format close to your default short or long date formats. These formats are marked with an asterisk (*) in the *Format Cell* dialog window and you can quickly access them on the Excel ribbon (*Home* tab > **Number** group):

You will be able to easily change the date format later via the *Format Cells* dialog that opens on the Ctrl + 1 shortcut. For more details, please see How to change the date format in Excel.

**Note.**If a date you've entered displays as a number of pound signs (#####) in a cell, most likely the cell is not wide enough to fit the entire date. To fix this, double-click the right border of the column to auto fit the date, or drag the right border to set the desired column width. If this does not help, please check other Excel date format troubleshooting tips.

### Inserting today's date and current time in Excel

In Microsoft Excel, you can input the current date and time either as a static or dynamic value.

#### Shortcuts to enter today date in Excel (as a timestamp)

To begin with, let's define what timestamp is. Timestamping is entering a "static date" that won't change with the course of time or when the spreadsheet is recalculated.

So, if your goal is to enter the current date and/or time as a static value that won't automatically update the next day, you can use one of the following shortcuts:

- Ctrl + ; shortcut inserts the
**today date**in a cell. - Ctrl + Shift + ; shortcut inserts the
**current time**. - To enter the current date and time, press Ctrl + ; then press the Space key, and then Ctrl + Shift + ;.

#### Insert an automatically updatable today's date and current time

If you want to input today's date in Excel that will always remain up to date, use one of the following Excel date functions:

`=TODAY()`

- inserts the**today date**in a cell.`=NOW()`

- inserts the**today date****and current time**in a cell.

Unlike Excel date shortcuts, the TODAY and NOW functions will always return today's date and current time.

When using the Excel date functions, please keep in mind that:

- The returned date and time are not refreshed continuously, they are updated only when the spreadsheet is re-opened or re-calculated, or when a macro containing the function is run.
- The functions take the current date and time from your computer's system clock.

#### How to insert today date & current time as unchangeable time stamp

This section addresses a handful of comments that have been posted on this page with one and the same question - *"What formula do I use to enter a timestamp in my Excel sheet without it changing every time the worksheet is reopened or recalculated?"*

For starters, I'd like to note that I'm very hesitant to post the solution because it involves circular references, and they should be treated with great care. Anyway, here goes the formula…

Let's say you have a list of items in column A, and as soon as a certain item is shipped, you enter "Yes" in the Delivery column, which is column B. Once "Yes" is in there, you want to have the current date and time automatically inserted in the same row in column C as a static unchangeable time stamp.

To do this, we are going to use the following nested IF formula with circular references in the second IF function:

`=IF(B2="yes", IF(C2="" ,NOW(), C2), "")`

Where B is the *Delivery* column, and C2 is the cell where you input the formula and where the time stamp will eventually appear.

In the above formula, the first IF function checks cell B2 for the word "Yes" (or any other text you supply to the formula), and if the specified text is there, it runs the second IF function, otherwise returns an empty string. And the second IF is a circular formula that makes the NOW function return the current day and time if C2 doesn't have a value in it already, thus saving all existing time stamps.

If instead of checking for any specific word, you want the timestamp to appear when you put anything in the specified cell (that could be any number, text or date), then have the first IF function to check for a non-empty cell, like this:

`=IF(B2<>"", IF(C2="" ,NOW(), C2), "")`

**Note.**For this Excel circular formula to work, you should allow iterative calculations in your worksheet. Also, please keep in mind that there are many reasons not to use circular references in Excel, and if you decide to utilize this solution in your worksheets, it's on your own risk.

### How to auto populate dates in Excel

If you need to insert dates in a range of cells, you can let Excel "auto date" a column or row by using the AutoFill feature.

#### Auto fill a date series that increases by one day

To automatically fill a column or row with an incrementing date series that increases by one day, you use Excel's AutoFill feature in the usual way:

- Enter your initial date in the first cell.
- Click on the cell with the first date to select it, and then drag the fill handle across or down the cells where you want Excel to add dates. The fill handle is a small green square that appears at the bottom-right corner when you select a cell or a range of cells in Excel, as shown in the screenshot below.

#### Auto fill weekdays, months or years

There are two ways to automatically populate the selected range of cells with weekdays, months or years.

- You can use the Excel AutoFill options as described above. When the range is populated with sequential dates, click the
*AutoFill Options*icon and select the option you want:

- Another way is to enter your first date, select that cell, click the
**right**mouse button and drag the fill handle down the cells you want to auto fill with dates, and then release it. When you do, Excel displays a context menu and you select the appropriate option from it.

#### Auto insert every 2^{nd}, 3^{rd} or N^{th} day

If you've tried a second solution described above, you probably noticed a whole lot more Excel auto date options the fill handle provides. One of them is inserting every 2^{nd}, 3^{rd}, 4^{th}, etc. day, month or year in a worksheet. Let's try this now:

- Add the first date in some cell.
- Select that cell,
**right-click**on the fill handle, drag it down or across several cells, and then release. - In the context menu, click
**Series**. - In the
*Series*dialog box, choose the appropriate*Date unit*and enter the*Step value*.

#### How to inset random dates in Excel

Regrettably, Microsoft Excel does not provide an option to enter random dates automatically. Luckily, AbleBits Random Generator for Excel does :)

You simply select a range of cells where you want to autofill dates in a random order, and switch to the Random Generator's pane where you specify:

- Start and End date;
- What days to add - weekdays, weekends or both;
- To add only unique dates, check the
*Unique**values*

Then you click the *Generate* button, and have the selected range populated with random dates.

Apart from dates, the Random Generator add-in can auto fill your worksheets with numbers, Boolean vales and custom lists. If you think this is something that would be useful in your work, we will gladly provide you with a 15% promotion code that we offer exclusively to our blog readers: AB14-BlogSpo

## Insert a date in Excel via a drop-down calendar (Date Picker)

If you are setting up a spreadsheet for other users, and want to make sure they enter dates right, it may be a good idea to insert a drop-down calendar in a worksheet. Your users will be able to fill in dates in a mouse click and you will be 100% confident that all dates are entered in an appropriate format.

If you are using a **32-bit** version of Excel, you can use Microsoft's Date Picker control. For the detailed instructions, please see How to insert calendar in Excel (Date Picker control).

If you are using a **64-bit** version of Excel 2016, Excel 2013, Microsoft's Date Picker control won't do. In this case, consider using one of the third-party calendars, for example our own one :)

For more options, please see third-party drop-down calendars for Excel.

This is how you insert date in Excel. I am hopeful these date entering techniques, shortcuts, functions and Excel auto date features have proved useful to you. Anyway, thank you for reading!

I have a problem please give me a guide how to solve.

i want update every day automatically pending days anyone help me

Hi,

i like to know if i can get a list of day and date in separate columns if i enter a third column with the current month. And every month if I change the month and year, the day and date should also change.

Please I am trying to use excel as a time sheet for HR. I want to be able to calculate the actual time worked for each day, while deducting break periods. Break time however is deducted based on number of hours worked, e.g for 5hours or less it is 20mins break, 6 to 8 hours it is 25 hours and so on. Please help.

Thanks

hi need help in excel formula:

I want to auto date my column/cell.

if B1 is 1, Autodate A1.

I will appreciate your help. Thanks

Hello,

I am am working with months, days, and numbers (not dates). I am wondering if there is a formula to recognize all 'Mondays' per month? In this case I will not have to select each cell manaully for a new month.

am trying to create a phone log for a busy office . I need the date and time to auto fill when I take a call to record the callers information and nature of their call . I cannot seem to get it working to autofill. Any help is much appreciated.

I have quarry Ex: If have entered a date in A3 as 01-01-16, and i would like to know the correct date of 6th Month in B3, like showing as 01-06-16. can u help me with the formula

Hello Munwar,

You can use the following formula:

=DATE(YEAR(A3), MONTH(A3), 6)

Dear expert,

I have quarry that i selected two raw but + mark no showing right side of row

so that i have not drag date, please suggestion for setting ??

Good morning. I'm using the =IF(B2"",IF(C2="",NOW(), C2),"") formula and it's been working fine for a long while. Now all of a sudden it stopped working even though the formula is unchanged. I just get the circular reference warning. Any ideas on why and how to fix it?

Can I make an entry in one like cell A and excel automatically gives me the date and time I made that entry in cell B??

Hello Ms. Cheusheva,

Thank you for this helpful post. I was wondering is there a way to have cells auto-populated with a calendar date series based on the day of the week?

Ex: Friday: [07-Oct-16] [14-Oct-16] [21-Oct-16] [28-Oct-16] [04-Nov-16] etc

Thank you so much!

Hello Tinker,

You can use the "Series" auto-fill feature, as explained in "Auto insert every 2nd, 3rd or Nth day":

- Enter the first Friday date in the top cell.

- Select that cell, right-click on the fill handle, drag it down to as many cells as you want, and then release.

- In the context menu, click Series, and set the Step value to 7, telling Excel to auto fill every 7th day. Done.

Hello Ms. Cheusheva,

Nice work.

Hi Ms. Svetlana Cheusheva,

How can I make the date and time update automatically?

For example:

"The P/N ########## was right based on Agile on 10/20/2016 @ 8.00" is in 1 cell.

The "10/20/2016 @ 8.00" need to be updated based on current date and time.

Hi

I want to insert only sundays of a year in excel how to do it ?

Kindly help me

Hello Arham,

You can use the "Series" auto-fill feature, as explained in "Auto insert every 2nd, 3rd or Nth day":

- Enter the first Sunday date in the top cell.

- Select that cell, right-click on the fill handle, drag it down to as many cells as you want, and then release.

- In the context menu, click Series, and set the Step value to 7, telling Excel to auto fill every 7th day, i.e. only Sundays.

I want to input the date as 30.12.2016, but system does not recognize as date. Please support.

Hi Kalwar,

For the system to be able to recognize a date, enter it in the default format (one that displays on the Home tab, in the Number Format box, for Short date), and then apply the following custom date format to the cell: dd.mm.yyyy

I have entered date unevenly

A1=10/5/16

A2=5/01/2016

A3=30/6/2016

How can get them ranging from jan to dec.??

Hey, Svetlana, lots of thanks for your effort.

you have gave description how can we make timestamp for interring value or value change in a cell directly. But this formula don't work for whose cell, that's value is change through link.

Suppose, I have to record timestamp in cell B1 where value of cell A1 is changed. Here, cell A1 is linked with (A1=C1+D1) cell C1 & D1. is this formula works for timestamp in this circumstances. I don't think so:(

Is there any function available to record timestamp of a linked cell value change?

Your urgent feedback will be highly appreciable. :)

Hi Ms. Svetlana Cheusheva,

I have a set of data on sheet 1 and I have a search box made for the data in sheet 1 I have created the below Macro but I can't get it to run on my workbook

I would like the macro to start searching in sheet1 in row 4 for a chemical name in column C or product code in column D

and if the term in Column C or D matches I want it to copy the whole row to sheet 2

please advise

Thanks

'If value in search_box = Matches anything in column C or D, copy entire row to Sheet2

Dim LSearchRow As Integer

Dim LCopyToRow As Integer

'Start search in sheet1 row 4

LSearchRow = 4

'Start copying data to row 2 in Sheet2 (row counter variable)

LCopyToRow = 2

'Select row in Sheet1 to copy

Rows(CStr(LSearchRow) & ":" & CStr(LSearchRow)).Select

Selection.Copy

'Paste row into Sheet2 in next row

Sheets("Sheet2").Select

Rows(CStr(LCopyToRow) & ":" & CStr(LCopyToRow)).Select

ActiveSheet.Paste

'Move counter to next row

LCopyToRow = LCopyToRow + 1

'Go back to Sheet1 to continue searching

Sheets("Sheet1").Select

End If

Next I

please advise thanks

hi madam

we unable to get in formulated cell , what can we do for getting date

My receiving group documents daily incoming materials on spreadsheet. They have to write the date for everything. Is there a formula that can auto populate the date once they enter data on that row. I tried =if(C1=",NOW()*C1). but this did not work?

Hi, I would like to know how to make a cell automatically show the next July 1st from another's cell's date shown. In other words, I have a due date that is always July 1st, so I want the formula to automatically display the next July 1st from the date I input in the preceding cell.

So if A1 says (01/01/2016), I want A2 to automatically display (07/01/2016), but if B1 says (07/02/2016), then B2 should display (07/01/2017).

I have tax invoice template set in Excel, is there a way that the date or print out date is auto generated?

Hi,

I've tried auto-filling a column of dates, but it increases the year for each cell (i.e. 5/12/16 -- 5/12/17 -- 5/12/18) instead by day. On the 'autofill options' drop down list there aren't the options for fill days, weekdays, months etc.

Any advice? Thank you

Can you explain the formula for getting the years between two days?

Example: The number of years between today and Dec 1-1960

Thanks for your help

This is exactly what I was looking for.

Thank you!

how to in cress date automatically. example - A1 -TODAY , in B1- i need next day date

What formula to use if you wants to know age calculation.

E.g. born on 15th May 2010 and I want to auto calculate age to the date of 31st Dec 2020 ?

Please help. Thank you

Hi, Svetlana.. Thank you so much. This really helps me a lot !

Hi I need a date selection list like calender to select the date where we can select any date & search the date. Is that feature is available.

Hello possible to enter a number auto copy paste into Excel from the site in

Different time

Hi what is the formula for calculating the number of days from today's date and the date selected..thank you!

Is it possible to automatically add a new column with the current date in front of column "B" everyday at a specific time?

For example, at 2am PST today column B would become column C and a NEW column would be column B that would auto-populate with today's date (Monday January 30, 2017.)

could not calculate years entering date at two cells,as the answer is '#value' comment 'with wrong date type'. Kindly help.

I need your help with regards to a simple query and tell me if it is possible.

I have a data sheet what i need is that if I enter any value in A1 it automatically updates the current time in B2 which doesn't change later on and stays permanent so i should know at what time that entry in A1 was made. Your prompt response will be highly appreciated.

Is there a way that I can see what date I inputted data into a particular cell in a worksheet without having a separate column for a date (e.g to see what when a payment was made)

How to do that if I fill the cell by numbers or touch the cell, next cell should be filled by current date automatically..?

HEY EVERYONE,

I JUST WANT TO PUT A DATE IN ONE CELL AND WANT THE OTHER 6 OR 7 CELLS SHOW THE PREVIOUS DATES IS IT POSSIBLE IN EXCELL

Hi to all. I need to put DATE, CURENT TIME in separate columns. Date and time had to be current(from computer clock) BUT unchangeable.

how to do that?

thanks

I want to have each cell in a column have a drop down list box that only includes the current time up to 23:39????

the same with other comment "I need your help with regards to a simple query and tell me if it is possible.

I have a data sheet what i need is that if I enter any value in A1 it automatically updates the current time in B2 which doesn't change later on and stays permanent so i should know at what time that entry in A1 was made. Your prompt response will be highly appreciated."

Hi,

I tried your following formula but it returned 0/1/1900 0:00

=IF(B2="yes", IF(C2="" ,NOW(), C2), "")

Appreciate if you can point out where the problem could be.

Thanks and Regards

Hi, Sunny,

to help you with your task, we need to know what you entered into the cells. You can try to explain here in more details, or send us a small sample workbook with your source data and the result you expect to get to support@ablebits.com. Don't forget to add the link to this article and your comment.

How do you put the current (automatically updating) date in the footer of an excel document, not in numbers but in words (example March 24, 2017, instead of 3/24/2017)?

Hi Monae,

you will need a VBA code to do that, look for some answers on MrExcel forum.

Using the + (plus) symbol does not work. (I used the + symbol on my numeric keypad.) Rather, using the = (equal) symbol works fine.

Hi,

i want to create a form for multiple employee for stock inventory. so i want if any employee enter his emp.code than his last balance auto show in excel form and if he give material request then automatically calculate from his last available balance.

Can you help me please

I generate reports on a daily basis, in cell AH60 I have =NOW() In Cell I56 i have =AH60 formatted to read yymmdd. What I want to be able to do is have it read yymmdd-### (ex.170331-001) with the number of my choosing to generate a report number. how can i add it. If tried to make it in the custom area but it keeps telling me its an invalid format...HELP!!! Please

Hi, Daniel,

unfortunately, custom settings won't help here, try using something like the following in the cell:

=TEXT(I56,"yymmdd")&"-"&ROW()

You can change the last parameter to make it return whatever you wish. Hope it will be of use!

I write a date in a column and want to automatic update of date when I open the sheet in next days. how can I do this.

Hi, vinod,

if you want the document to show you "today's date" (e.g. the date of your working with the file), try using the following formula:

=TODAY()

Hi All,

I am currently working a excel formula to input a Revision_Date in column A then it will auto generate the number of days per month(only weekdays) on column B(January), column C(February) and so on. Can someone help me as I am really not familiar with excel. Hoping someone can share any formulas/techniques on how to do it. Thanks in advance.

Hi All,

I am currently working a excel formula to input a Revision_Date in column A then it will auto generate the number of days per month(only weekdays) on column B(January), column C(February) and so on depending on the current date. Example if today is April 17, 2017 and my input in Column A is Feb 13, 2017, it will compute number of days from Feb 13 to Feb 28 (which is 12 days) to be generated on Column C(Feb). Then on March which is complete since it covers the whole month until today on Column D(Mar). Then comes to April to compute the days from April 1 to April 16 on Column E(Apr). Can someone help me as I am really not familiar with excel. Hoping someone can share any formulas/techniques on how to do it. Thanks in advance.

Hi, Gerry,

for us to be able to help you better, we need to see how the columns are named and arranged. Please, send us an example of your workbook with the source data and the result you want to get to support@ablebits.com.

Can I insert the start date of year in cell .. A1 then show me the end date of year in cell A2

Ex.

A1=1/1/2017 A2=31/12/2017

Greetings,

Hi would like to know from You

I Set date in my excel book and i want a formula that work with date for example

today 1-1-2017 and my figure is 100

next day when i open my log date will be 2-1-2017 and figure turn to 200 automatically.

Please help for this issue

Hi,

I want to link word file to excel is it possible if yes then ow it is possible i want to share data excel to word if its possible please guide me. Thanks

My excel inserted a row when I pressed CTRL +...OH WELL

How would I go about having row 1 be double dates in series for as long as I drag, i.e. 1 June, 1 June, 2 June, 2 June, 3 June 3 June. So every 2 columns are the same date?

hi Svetlana Cheusheva

m vijay

i use excel spreadshit fir entering lots of nmbers and party names date etc can u tell me solution i want to ask

1. how to autofill when iinsert party name then pary pace automatically in next coloumn

2. if i save my document then can u tell me each time when i save documrnt then save other place in specific path and where i work in that current old sheet is there like previous means when i save document then its automatically save another place where i want but my current formate is there like privous

mail me solution

time should change automatically in excel. Any formula for that Action.

=now()

Hi Svetlana,

I have lists of people with their dates of birth, and I want a second column to automatically calculate their ages without having to update them all manually. Is this possible, and if so, how do I do it please?

Cheers

HOW CAN I CHANGE DATE & TIME AUTOMATICALLY WHEN I OPEN EXCEL SHEET ?

Hi,

When I am converting a date time column to the name of the day by using the custom dddd function, the column is showing the day name (like Wednesday) but it's reading it as the same date time (when I click on day name the top space is showing the date time. So, I am unable to separate weekdays and weekends as during filtering its showing numbers and not texts.

How do I enter all dates from today till say next 20 years or infinite years.

How can I enter like this SATURDAY 01 JULY 2017 in excel 2007 with DATE FORMAT so that I can autofill the full month like SUNDAY 02 JULY 2017 MONDAY 03 JULY 2017

Hello, if I enter a specific date into a cell, how do I get it to autopopulate automatically in the following cells, then also show the day of the week on the calendar below?

Hi,

I am trying to Highlight the dates in excel if expire date is today and tomorrow and Past date should be red and Day after tomorrow it should be amber

Also it has to check the cell is empty or not Is this possible, and if so, how do I do it please?

i want to put multiple chooses not only YES like YES,NO,LATER

I want to know how to add date and day in same cell.

Like 08-08-2017 : TUESDAY

Please help

I'd like a formula to auto fill dates in a column....say c7-c26 when I manually change a "week ending" date in e4

By the way, great site.

In Excel, I have the date in one cell (05/09/2017) and in another cell I have the time (01:43:00 PM).

How can I combine both these to show, for example:

05/09/2017 01:43:00 PM

in the one cell so I can do date and time arithmetic?

I have set up a custom format (ddd, mmmm dd, yyyy hh:mm:ss) to display the result already.

Many thanks.....

Hello, Greg,

supposing that A1 contains date and B1 - time, use the following formula:

=VALUE(A1)+VALUE(B1)

If you need to combine them with the format, please try the following:

=TEXT(VALUE(A1)+VALUE(B1),"ddd, mmmm dd, yyyy hh:mm:ss")

My Excel does not run as yours, my date fills or automatically re-copy a single date all the way down of the spread block, or if I choose two consecutive dates as my starting block then it simply fills automatically, but increments only the year...

What do I have to set or reset?

Can I insert the start date of year in cell .. A1 then show me the end date of year in cell A2

Ex.

A1=1/1/2017 A2=18/01/2017

hi! so i am making a graph and the dates are not lining up with what I inputted into. ie

26-Sep

29-Sep

03-Oct

06-Oct

10-Oct

13-Oct

17-Oct

20-Oct

25-Oct

but it gives me every two days from the start date, just wondering how i could fix that.

thank you for your time

Hi please help,

Im same formula apply but time not peck always shown 00:00 or 12:00:00

Thanks Dear

Hi,

How to cress the date automatically.

For example if the

A1 column contains todays date (01/01/2018) then A2column/B1row should contain the next days date (02/01/2018) but the next days date should not be displayed in the sheet for today (01/01/2018)

Can anybody please help me with this??

I have a series of cells (7-11) that when the task completed I put a date into that cell. I have a % cell that I want to show the % completed. Example: I have 7 total cells and 3 show the date completed and % of the total is 21%. How can I shoe the % automatically?

If I give the date in Excel sheet the day has to be updated accordingly. Can you guys please let me know the formula.

Example: if I enter 2/27/18 then Tuesday has to be updated.

Hello, Yash,

If your task is to get a day of the week from your date 2/27/18, please enter one of the following formulas in the adjacent cell:

=TEXT(A1, "ddd")

=TEXT(A1,"dddd")

Where A1 is the cell that contains your date. The first formula displays the short form of the day, i.e. Tue, and the second formula returns the full day name, i.e. Tuesday.

Please also note that the day names you'll get after applying the above formulas will have the text format.

Hope this is what you need.

Hi,

If I have a date of 1-Mar-18 in a cell and want to auto calculate the 4 weeks in the month, how do I do so? I want to be able to input the month and year and have the work weekdays auto populate

Thank you- this site is amazing - was able to fix the problem I had so quickly and now have a shortcut to use continuously.

Hi,

I have an existing sheet having date and time filled automatically when i enter the serial number in A cells and go to B cell the date and time automatically fills in B. Can you please tell how to make it happen. since i want to make another sheet of same kind.

Thank you

Faizan

Auto day to day update DATE in excel work sheet

Hi Svetlana

sorry to disturb with small but teasing problem

Tried to ask friends and surf net … ;(

Where to look ?

It seems my computer wants (mac e 2011 and High Sierra.)

to show dates in decimal ???

Also in Format Cell it gives sample 1.1.1904 or 1900 depending which tick is in calculations box.

Näyttökuva 2018-6-6 kello 11.34.43.png

In my mind I have not changed anything in excel or mac. problem continues

Would appreciate a hint what now.

Cheers form Finland

Viljo:

I don't know much about Macs but I think I found a link that includes and article that might help.

https://support.microsoft.com/en-us/help/214330/differences-between-the-1900-and-the-1904-date-system-in-excel