The commentary says "happy birthday to me," but the picture... doesn't convey that. :/

The IJN Ryuujou was laid down on the 26th so we're getting close.
Or is it the artist's birthday?

FJH said:

The IJN Ryuujou was laid down on the 26th so we're getting close.
Or is it the artist's birthday?

The artist. His Pixiv profile says his birthday was the 20th.

Shipgirl birthdays are generally their "Launch" date as far as the vast majority are concerned. Their "Laid Down" date is more like when conception happened.

RJ's launch being all the way back on April 2nd.

Either way though, this image depressingly hurts my soul.

Tapper said:

The artist. His Pixiv profile says his birthday was the 20th.

Same as me then.

And I didn't even notice it was my birthday until my bank sent me a SMS to congratulate it.