Get the day change point(s) between two UNIX timestamps

I have the date range (two UNIX timestamps) and I need to find point(s开发者_JAVA百科) at 23:59:59 if exists. How I can do it with Perl?

P.S. I think for() is not good idea because I can have very big range. Anything another variants?

I would use Date::Calc. Suppose your two timestamps are located in $ts1 and $ts2:

use Date::Calc qw(Time_to_Date Date_to_Time Delta_Days Add_Delta_Days);

my @date1 = (Time_to_Date($ts1))[0..2];
my @date2 = (Time_to_Date($ts2))[0..2];
my @midnights;

for (my $i = 0; $i < Delta_Days(@date1, @date2); ++$i) {
    push @midnights, Date_to_Time(Add_Delta_Days(@date1, $i), 23, 59, 59);
}

@midnights now contains the UNIX timestamps (epoch seconds) of all 23:59:59 point(s) between the two given timestamps.

Disclaimer: Of course you could also do it with DateTime.

That's a generic algorithm. X is the 1st timestamp Y is the last one

1) Get the first change date, Z.

If Z > Y , there is no change.

2) Get the last change date, W

   If W = Z, there is only one change date.

3) Get the range of dates, R. Considering the range of one day is D

   R = W - Z .. The number of points will be the integer of (W - Z)/D

use DateTime;

Here's an example I scrapped together based on my semi-recent knowledge of the UNIX timestamp (school is such a long time ago...)

while (entry) {
   if ((timestamp-1) % 86400 == 0) {
      #match
   } else {
      #nomatch
   }
}

However, like everybody else, I would suggest using other tools to do that since my example does not take leap seconds into account and I highly doubt it's POSIX-compliant. More info here.