Yes I see your restriction against using Date::Manip, and I'm not going to bother asking what that's all about, but in the event someone else comes upon your question (which is the purpose for posting it into Q&A, right?), they may not have such restrictions placed on their development. In such a case, the following code might be useful: 
use Date::Manip;

$diff = &DateCalc("now", "21st at midnight");
$seconds = &Delta_Format($diff, 0, "%st");

[download]
You can certainly use other modules such as Date::Calc, but it will require additional logic.

In reply to Re: How to get time in seconds from localtime(time) to next 21st date of the month? by Fastolfe
in thread How to get time in seconds from localtime(time) to next 21st date of the month? by basman

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