Dates and time are stored as numbers but displayed as dates/time will 0
being 1/1/1900 at midnight.
The formula =RANDBETWEEN(30000,40000)+RAND() will generate a random date
between 18 Feb 1986 and 6 July 2009 with random time. You will need to
format the cell to see date and time. Press F9 to get a new values.
best wishes