I'm trying to learn what date a moon phase guide represents. For example, I don't know if the New Moon on Feb 26th means there's no Moon on the night of the 25th / morning of the 26th, or the night of the 26th / morning of the 27th.
I believe the way that it works, is the the time at which it peaks/goes darkest is marked as the day that it happens.
In this case, on Feb 26th, according to this page, the New Moon will peak at 14:58 UTC.
In other words, you're better off using a resource that doesn't just say the day but the actual time. Then depending on where you are in the world will determine if the New Moon peaks closer to the night prior or the night after.