Word Choice – Does ‘Have Good Holidays’ Sound Weird?

I've heard congratulations used in birthday greetings, or in wishing someone a happy new year, but it's generally intended to be somewhat humorous.

When I've heard it used, the implication has been: Congratulations! You made it through another year. Put another way: It's been a whole year and you're still alive. Congratulations.

Some might consider such "congratulations" to be morbid humor, particularly if the person you are talking to is quite advanced in age.

As for saying,

"Congratulations, I didn't know that."

I'd be careful with that one. It sounds like a sarcastic remark given to someone who has just stated something obvious.

As for:

"Happy new year in advance"

that sounds normal and idiomatic to me. Another more casual way you could say the same thing is:

"Have a happy new year!"

By putting the "Have a" at the start of the remark, you're acknowledging that the new year is coming soon but is still a little ways away.

Not exactly. I have a good temper or I am good-tempered means that I don't get angry easily; if I have a bad temper or am bad-tempered it means the opposite. (Also, if I lose my temper it means that I get angry when I tried not to; if I keep my temper it means that I managed not to lose it, despite being provoked.)

Now, I'm in a good mood (note that we don't say I have a good mood) means that I'm feeling happy at present; I'm in a bad mood means the opposite. Also, a person who is moody is someone whose mood changes easily, from good to bad and back again.

So, a person's mood (the mood that a person is in) is how they feel at a given time, whereas a person's temper is how they control their anger in general.