Dates with periods in Excel can be a bit tricky to work with. Here are some tips to help you get the most out of them:

• When entering dates with periods in Excel, always use the format yyyy-mm-dd. This will ensure that the date is interpreted correctly by Excel.
• If you need to enter a date range that includes a period, use the yyyy-mm-dd/yyyy-mm-dd format. For example, if you want to enter a date range from January 1st, 2016 to January 31st, 2016, you would use the format 2016-01-01/2016-01-31.
• You can also use the yyyy-mm-dd/P format to specify a date range that spans multiple months or years. For example, if you want to enter a date range from January 1st, 2016 to December 31st, 2016, you would use the format 2016-01-01/P12M. The P12M portion of the format indicates that the date range spans 12 months.
• If you need to enter a date with a time component (e.g. 9:00 AM), you can use the yyyy-mm-dd hh:mm:ss format. For example, if you want to enter January 1st, 2016 at 9:00 AM, you would use the format 2016-01-01 09:00:00.

• Note:

  The formats described above are just some of the most commonly used formats for dates with periods in Excel. There are many other formats that can be used - see Microsoft's documentation on date and time formats in Excel for more information.