Lengthens the free-running period of the locomotor activity rhythm from 24 to 27 hours under constant darkness by lengthening both active and rest phases equally. Heterozygotes with tim+ have slightly longer periods than wild type strains or timY3501 homozygotes. timY3502/timY3503 transheterozygotes have a period of 27 hours under constant darkness.
timY3502 and timY3503 could have identical mutation(s).