First, use binding valuables, so your queries become:

delete from now_time where lasttime < ?
delete from day_time where lasttime < ?
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This is a suggestion for the future. But for this particular case, what you should really do is to calculate the time difference by using MySQL internal functions, not to calculate in Perl and pass to MySQL.

Read MySQL document and look for the section for date and time functions. Pay attention to ADDDATE(), ADDTIME(), CURDATE() and CURTIME(). Your query should become something like:

delete from day_time where lasttime < CURTIME() - INTERVAL 1 DAY;
delete from now_time where lasttime < CURTIME() - INTERVAL 5 MINUTE;
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