Postby thegooseking » February 10th, 2017 5:02 am
Jason-san,
Your first sentence, ハッピーバレンタインデー isn't Japanese: it's just the English "Happy Valentine Day" written in katakana. However, even if it's English, a phrase like that will be used in Japan quite commonly. (Note that in Japanese it's Valentine Day, not Valentine's Day, but that's the only real difference.)
However, a (slightly) more natively Japanese way you could say it is:-
バレンタインデーおめでとう (barentain dē omedetō)
(Or バレンタインデーおめでとうございます (barentain dē omedetō gozaimasu) to be more polite.)
おめでとう often means "congratulations", but it's more generally a statement of "this is a good occasion". It's often used for Happy New Year (あけましておめでとう - akemashite omedetō), and Happy Birthday (おたんじょうびおめでとう - o-tanjōbi omedetō), but I have seen it used for Valentine's Day, too.
I'm not sure about your second sentence. I don't think it's common to use 幸せ (shiawase, which literally means "happiness") as a greeting. It could be translated as "Valentine's Day of happiness", but using "happy" to celebrate an occasion is English thinking that doesn't necessarily translate to other languages. I also don't think it's common to use 日 for what you might call "borrowed" holidays (though it's definitely used in the names of natively Japanese holidays).
小狼