Tenses

[rajeshmalladi]

They have left before it has snowed.
They have left before it had snowed.
They had left before it has snowed.
They left before it has snowed.
The left before it snowed.

Please explain the differences between the above sentences.
Thanks,
Rajesh.

[Pete]

They have left before it has snowed.
They have left before it had snowed.
They had left before it has snowed.
They left before it has snowed.
The left before it snowed.

Please explain the differences between the above sentences.
Thanks,
Rajesh.
A. They have left before it has snowed. [Not correct.]
B. They have left before it had snowed. [Possible. Means the same as E. E is preferred.]
C. They had left before it has snowed. [Not correct.]
D. They left before it has snowed. [Not correct.]
E. They left before it snowed. [Correct. This is the best form.]