regarding the behaviour of gmtime() Linux system function

[treuss]

This problem seems to be weird.

At one execution of my program, time increment works fine, but on another run of my program at a later time, it does not. (I run it with the same user)

I'm not 100% sure if this is the problem, but you are not setting timeinfo.tm_isdst, which means the value of the field is undefined when calling mktime. Try explicitly setting timeinfo.tm_isdst to -1 (information not available) to have the system try to figure out itself whether DST is in effect or not.

What do you mean by wormhole and how can I check for them ?

They look something like this.