Faq/Calc/018/en

How to insert a variable date into a cell
Insert a function into the cell, following these instructions:
 * 1) Select the desired cell.
 * 2) Go to.
 * 3) In the Categories list, choose Date and time.
 * 4) Click on TODAY to get the current date or NOW if you also want to write the hour.
 * 5) Click on Next.
 * 6) Click on OK.

Since version 3.6 of LibreOffice you can also insert the date as a field:
 * 1) The cell must be in the Edit in place state (double click in the cell)
 * 2) Right click, choose

If you do not want the date to be updated, use the keyboard as follows:
 * to insert the date.
 * to insert the time.