Past Tense (과거) -았/었어요

Conjugating past tense is pretty easy, especially if you know how to conjugate the POLITE PRESENT TENSE! Basically all we need to do is add -았(다) or -었(다)  to the verb stem.

POLITE PAST TENSE 

1) Take the dictionary form, drop the 다 so you are left with the verb stem.
2) Add the ending 아 or 어 following the rules we learned about present tense
3) Add ㅆ under the last syllable (아/어 => 았/었)
4) Add 어요 afterwards (after attaching 았/었) .

So the basic rule is this:

If the final vowel is ㅏ or  ㅗ then you add +았어요 .
가다 =>갔어요 (to go)
자다 => 잤어요 (to sleep)

If the final vowel is NOT ㅏor ㅗ then you add +었어요.
먹다 =>먹었어요 (to eat)
배우다 => 배웠어요 (to study)

All the verbs that end in 하다, conjugate to 했어요.

FORMAL PAST TENSE

Now that we know how to form the polite past tense, the formal conjugation pattern is even more easier to explain. 

Here is the basic pattern.

1) Take the conjugated polite form (ie 갔어요, 먹었어요)

2) Drop the -어요

3) Add -습니다 instead .

Base Form	Formal
가다	갔습니다

Base Form	Formal
먹다	먹었습니다

CASUAL PAST TENSE

Casual speech is pretty straightforward.  You simply remove the -요 from the polite form speech