Wah How to use It's about time.

We know how to use It's time but it's different than It's about time.
We use It's (about) time + Past tense to talk about something you should have done in the past but you didn't do it in that time. (It is almost too late.)

• It's about time he got a haircut. (Your hair is too long. You should have cut it 3 weeks ago, then you should get a haircut now.)
• It's about time you paid me. (It's 2 month late and you haven't paid me so far, you should pay me right now.)
• It's about time I started learning English.
• It's about time we had a break.
• It's about time you cleaned your shoes.

Note: We don't have to put about in the sentences
          It's time he got a haircut. 
          It's time we had a break.

Let's see the difference between It's time and It's about time.

• It's time for you to wash your car. (Your car is a bit dirty, you should wash it right now.)
• It's about time you washed your car. (Your car is very dirty. You should have washed it last week ago, then you should wash it right now.)

It's about time you get some new clothes.