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.
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_________________
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.

[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