DAY: idioms +

Phrase a day in which something important or exciting happens
big day
It was a big day for Bandar and Sukacita. The two tiger cubs learned to swim the hard way—by getting dropped in the water!
Phrase in small amounts every day
day by day
Day by day my English speaking skills are getting stronger!
Phrase for a time in the future when something will be needed
for a rainy day
At the end of the week I put any extra cash I have in a jar in my room. I'm saving it for a rainy day.
Phrase a time in the past that is remembered for great success or happiness
glory days
My neighbor has a trophy case in his house filled from his glory days as a star athlete.
Phrase an especially tiring or stressful day
long day
A. How was work today?B. Don't ask! It's been a long day.A. I'll make you a cup of tea and you can tell me about it.
Phrase to cause someone's day to be pleasant or happy
made my day
Mark Ruffalo is one of my favorite actors. Meeting him made my day!
Phrase a day when something good will happen to you
wasn't your day
Hey now, don't feel bad for losing in the championship. Today just wasn't your day.