From the MozillaWiki:
Proposed Freezes ( All dates use time of 23:59 Pacific )
- Slushy String freeze date: 2009-04-24 (Friday)
- Slushy Code Freeze date: 2009-04-26 (Sunday)
- Firm String / Code freeze date: 2009-04-28 (Tuesday)
- l10n-mozilla-1.9.1 freeze date: 2009-04-30 (Thursday)
- Target Build Ship date: 2009-05-05 (Tuesday)
Not sure what’s after this if is going to be a Beta 4 or may be if we are lucky Release Candidate 1!