The more i hear about this spell, and the stipulations the DM has placed on it that don't seem to be inherent to the spell but to some Time councill thing, the more is sounds like this is a Narrative honeypot.

Or more simply, it is a trap meant to tempt people into break the rules for story possibilities. 
Could just be an aweful spell that DM is attached to though and i am reading too much into it. Sounds like it would be more balanced as a feature where this time angel can cast rituals in one minute instead of ten.

I actually thought about that, a ritual would have been better than a spell, and maybe it will get changed in the future. The DM assures all of that the spell is not there as a 'cheat' to let a certain player gain power over the rest. It was meant to be a 'tool' to aid in the player's quest to 'help'. The one thing you have to know about the 'angels' is they are much like the Nox in Stargate, they are for the most part pacifists. They don't share knowledge or tech, they don't interfere or attempt to lead another race in any certain direction. They attempt to remain neutral when it is possible. They are allowed to advise and protect, that's all. Nothing more than that. I agree that performing the spell in the way she wanted to, violates the non-interference and possibly the no-harm rule. She cannot under any circumstance, cause permanent harm or death to another being. It is encoded in her DNA. She can use her magic to disable (temporarily) a foe, but not do any permanent damage to them. It makes her useful in some ways, and useless in others, sort of a balance between the two. That is the way Time Angels are created. Just to let you know, this lady that plays the character is a long time friend of mine. She just wanted to play a character that can be helpful, but not too powerful. She isn't always able to attend the games. When she can't, she just states it as having to be on "council' duty for that day. It actually works out pretty good. She has no problem revising her character on-the-fly. She made it that way on purpose. I actually think she is going to revise that spell a bit. I'm actually going to give her your idea about making the spell into some sort of ritual that only the 'angels' can perform. That would certainly give her more leg room and would cut down on the confusion of using such a spell, thus it would bypass all the time travel stuff required by such a spell. You can do almost anything with a ritual, it works almost the same way as a curse does, at least mechanic wise.  I actually like that idea myself, wish I had thought of it back when I was a DM, maybe my NPC time traveler would have worked out better.I know it would have helped the story out for sure.