Group for a pre-defined period

Hello, drupallers!

Problem description: I need to assign some users from group1 to a specific group2 (f.e. extended access) for some period (month, year), than turn back to group1 (their previous group) automatically.

I still didn't found any solution here so not sure is this functionality already done in Drupal? (5.2 for my case)
Cron, Events, Actions modules doesnt looks ready to solve the proiblem, guess because I haven't enough experience in Drupal.

Thanks!