Which is correct and why? (We will be leaving for Mexico January 1st and will...)

[grammatically_correct]

1. We will be leaving for Mexico January 1st and will be returning January 27.

2. We will be leaving for Mexico January 1st and will return January 27.

[Mister Micawber]

.
Both are grammatically correct. The first is stylistically so.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber

[grammatically_correct]

Thx!

[aydincelenk]

Hi G-correct,
You should have used the preposition "on" just before "January 1st" although both sentences are correct.
_________________
If the blind lead the blind, both shall fall into the ditch.

[Mister Micawber]

.
On is OK, but not required. I'll see you (on) Tuesday.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber