her flanks look so good! I love Dashie so much!

@Cirrus Light 
Tumblr filenames use some kind of numeration with letters. For example, the first pic of 2014 with a Tumblr source was >>511529, and the original filename was tumblr_ myntyj1W5a1srdqwko1 _1280.png. The first pic of February 2014 was >>539937, tumblr_ n08vjsnaDP1r66jpfo1 _1280.png. And for the record, the most recent pic is >>1489036, and its original filename was tumblr_ orpl9bd68F1uuvdnio1 _1280.png. Alphabetically, myn... < n01... < n08... < orp..., so this pic was posted to Tumblr in January 2014.
 
I know it’s not a great clue, but it’s literally the only thing I could figure out from the pic, so I thought that it was worth mentioning.

@Background Pony #E74E 
Why does that file name imply that?
 
Jeez, finding this feels like a needle in a haystack kind of problem.

Found on /mlp/. According to the reverse search it wasn’t here, and I can’t find the source with Google Images either. Judging by the original filename (tumblr_n0ldd53R7m1qa7q25o5_r1_1280.png), it’s probably from early 2014.