On 4/13/22 06:30, Martins Ozolins via GNU coreutils Bug Reports wrote:
ozoma@ozoma-ThinkPad-X250:$ date +%s --date="1981-04-01" date: invalid date ‘1981-04-01’
This is because your invocation is equivalent to: date +%s --date="1981-04-01 00:00:00" and there was no midnight at that date in Latvia.