Man pages matching name test::mocktime::datecalc in section 3pm:

Test::MockTime::DateCalc.3pm.en	debian 10 / libtest-mocktime-datecalc-perl
Test::MockTime::DateCalc.3pm.en	debian 11 / libtest-mocktime-datecalc-perl
Test::MockTime::DateCalc.3pm.en	debian 12 / libtest-mocktime-datecalc-perl