There are basically two different notions of time generally accepted, one based on the physical rotation of the earth (one full rotation = 1 day), the other based on the SI second (a fixed, constant value). Think about it, a "UT second", as defined relative to the rotation of the earth, may have a different absolute length depending on the day!
Anyway, the fact that are based on UT seconds is a simplifying, yet honest assumption so that things like leap seconds and all their complexity can be avoided. Basing types on the UT second basically means that every minute has 60 seconds and every day has 24 hours and leads to more natural calculations when working with calendar dates. As few slots as possible are going to change, so we first increment the month slot by 1, 2014-03-28, and boom, we're done because that's a valid date.
characters let the parser know which periods to parse in each slot. In the module, it gives the result of February 28th. I like to think of the classic 7-7-7 gambling game in casinos. On the other hand, if we were to add 2 months to our original date, 2014-01-31, then we end up with 2014-03-31, as expected.
Fixed-width slots are specified by repeating the period character the number of times corresponding to the width with no delimiter between characters. Now just imagine that instead of 7-7-7, the slots are Year-Month-Day, or in our example, 2014-01-31. The other ramification of this approach is a loss in associativity when a specific ordering is forced (i.e.
All versions of Excel for Windows calculate dates based on the 1900 date system.
Excel 2008 for Mac and earlier Excel for Mac versions calculate dates based on the 1904 date system.
Excel 2016 for Mac and Excel for Mac 2011 use the 1900 date system, which guarantees date compatibility with Excel for Windows.
When you copy dates from a workbook created in an earlier version to a workbook created in Excel 2016 or 2011 for Mac, they will be converted automatically unless the option to "Automatically convert date system" is disabled in Preferences Date Options.
Or, you can keep the 1904 date system for the pasted dates only.
In the 1900 date system, dates are calculated by using January 1, 1900, as a starting point.
This is the default date system in Excel for Windows, Excel 2016 for Mac, and Excel for Mac 2011.
If you choose to convert the pasted data, Excel adjusts the underlying values, and the pasted dates match the dates that you copied.
If you choose not to convert the data and keep the 1904 date system, the pasted dates vary from the dates that you copied.