How does the passage of time work in the Ranma universe?
Using the anime as a reference, there have been 3 Xmas related episodes.
These were the Yutaro/panda episode, Xmas special and the  1st OAV.
Using these instances, I would presume that the cast to have aged 3
years. In the manga, would a change in teacher mean that a year has
past. Probably not. But I think that using Hinako as a time reference is
valid. However, Ranma and Co do not go to the next year, meaning that a
year hasn't past. Is there any instances or mentioning of any birthdays
in the manga or anime?

Eric
Custodian of the severed hair