1. Explain it simply
都 goes before a time, age, or amount to stress that it already seems late, old, or a lot.
The clause ends with 了, giving the whole thing the meaning 'already (so…)'.
The tone is emphatic or mildly complaining, like 'it's already this late!'
2. Show examples
都八点了，快起床吧。
Dōu bā diǎn le, kuài qǐchuáng ba.
It's already 8 o'clock, hurry and get up.
clock time
你都十岁了，可以自己洗衣服了。
Nǐ dōu shí suì le, kěyǐ zìjǐ xǐ yīfu le.
You're already ten, you can wash your own clothes.
age
我都等了半个小时了。
Wǒ dōu děng le bàn ge xiǎoshí le.
I've already waited half an hour.
amount of time
都十二点了，商店关门了。
Dōu shí'èr diǎn le, shāngdiàn guānmén le.
It's already 12 o'clock, the shops have closed.
emphatic tone
3. Share a tip
Put 都 before the time or amount and end the sentence with 了 — the pair adds an emphatic 'already' feeling. Don't move 都 after the point or drop the final 了.