How can I subtract two Date/time values in MS-Access?

Answer 1

The MOS instructor gave you instructions for EXCEL...

MS Office does treat dates as the number of days since 1/1/1900 where decimals are fractions of a day and equate to time. So .5 is noon

In Access create a select query in design view and add the table with your data (date fields)

Right Click on a field columns field row(top cell) and click build.
This will bring a pop up box where you can add a formular.

On the left side of this popup will be a list of data sources (Query Tables ect) brows through your data sources until you find the table with your data and double click it. You will now see a list of fields in the middle box. Double click each field you are interested in and build your function clicking on the + - / * symbols as needed to build your function. Click OK and run your query. (DATE1 - DATE2)

Access will treat DATES as the underlying DOUBLE number and return the answer as a number. The number is the number of days and fraction of a day. so 1/1/2006 - 1/1/2007 = 365.0
if you convert 365 to a date it will return 1/1/1901 because Dates are computed starting at 1/1/1900 .

Answer 2

Well, I'm not quite sure what your asking...
If it's what I think...put in the dates in say cell A1 and the next in B1...they should by default take the date format. Select both go to Format-Cells and in Categories choose General...when you return you'll see a long number with decimals and everything...this is called the Century Shift. Since January 1, 1900 each day has been counted so January 15, 1900 would be 15.25 if it's the first part of the day. Now click on cell C1 and enter the formula A1-B1 hit Enter on the keyboard. Now to return it to Date Format...go to Format Cells and change it from General back to Date and Time.
I hope that's what you meant. You can find out how many days old you are. And for Star Trek fans...that's what they mean by StarDate 899049.76 it's just in General format although I think they go from discovering Warp drive or from the First Enterprise...never got bored enough to figure that part out.