The first episode was on November 2010, but was set during the “Summer Sun Celebration”. And what about episodes like “It Isn’t the Mane Thing About You” that take place over several days, if not months? Do different airdate per country effect things?
 
It seems clear that real-life date are meaningless in this context.

Que bonita

Translation:
 
Rainbow dash Age 23 or 21 years old… born Feb 1 ‘93 or ‘95
 
In chapter 12 of Season 4 “Pinkie pride” she talks about her birthaversary, basing on the date of the premiere, Feb 1 2014, it could be her birthday, her cake had 21 candles which suggests that it’s her age (arguable) 21 years back takes us to Feb 1 1993, knowing Fluttershy’s age, they both used to study in Cloudsdale, if we ignore the cake candles and keeping in mind that that chapter 23 of Season 1 “Cutie mark chronicles” where Fluttershy is taller than Rainbow, we could suggest that Rainbow is 1 or 2 years younger than Fluttershy.