Pnut is 3ish. We moved her birthday up a couple of months so that we could have friends together at the nearby farm and ride her favorite pony. We are an urban family raising a farmer. Yesterday she just wanted to stay and watch the farmer clean out stalls, in other words shovel manure.
I moved my birthday years ago and it is has been so freeing. There was very little positive holding me to that date. Moving my birthday was freed me from those times.
I aim to have the most fun possible everyday and flexible birthdays fits with that very nicely. A farm birthday with her friends and favorite pony was perfect.