It's #HangeulDay ( #한글날 ). #Hangeul is a script that can be adopted & adapted for various languages far more precisely than Latin/Roman.

Here's Mabuhay Hangeul v1.0 (wip) for #Filipino in Hangeul. (v2 soon)

YourOnly.One wiki
#Hangul #HangulDay #Philippines #필리핀