i think it's a bug(a really small one!).
I've one Time condition "kids" and if i create a new firewall rule and if i therein try to choose the Time condition two are shown "Always" and "kids". If I now click on "kids" the edit-rules-site is shown again, but the Time condition is still the initial "Always". Ok, Submit!
After committing the rule and re-editing that one, I can choose the Time condition "Kids".
Hope my report is OK - otherwise tell me what to do better!