Check cron's nextrun date calculation

[4unkur]

in some cases this date is calculated wrong. It sets the nextrun time to 1 year ahead from the time that should've been set.

[4unkur]

I was able to reproduce the issue:
To get the incorrect calculation set the timestamp of 31 Jan 2018 23:55 (timezone should match)
in ia.core.cron.php in assignment: $dateArr = getdate(); (pass ts as param)
you'll get 1 Jan 2019.

Meanwhile I imported 3rd party parser: https://github.com/poliander/cron
it works properly and maybe we'll stick with this solution.