Subjunctive Past
The Subjunctive Past has two sets of endings, but are used exactly the same. (might)
When to use the Subjunctive Past
The Subjunctive Past basically has two uses:
1. Posibility or subjectivity with a past time frame.
Example:
Dudo que lo hiciera tan rápido.
I doubt that he did it so quickly.
2. A past time reference, hypothetical rather than actual.
Example:
Si tuviera más tiempo...
If I had more time...