Time? A very important aspect in the life of every individual. It spins and spins with no end in sight, dictating over elders and young alike.
Time is a process that all must go through irrespective of their strength or will. Even Sango is defined within the concept of time.
What then does it mean to be the God of time? It is a question that Sango could have easily provided an answer to if he was in the game world.
But no, this isn't the game world. This is a reality with an endless possibility to the ability one possesses, and the only restriction is the total mana one has in their mana pool.
Through a single ability, one can manifest branches through it by making use of their mana to cross-examine new abilities.
Ruby serves the God of time, or at least Sango believes that to be so from the ability she has displayed.