H4 to New H1B with Previous H1B Experience

[toreador923]

Hi,

Here's my situation:

1. I have had an H1B in the past with an employer for 6 years.

2. They did not file for a Green Card, and that H1B expired in May, 2010.

3. I went out of the country for a year and a half.

4. Came back in December, 2011 on H4.

5. Looking for H1B sponsorship in April.

If an employer files for an H1B in April, when is the earliest that I can start working for them?

Thank you!!!