3/20/2008 Spring Equinox 05:48 U.T.
30 day standard after the Equinox
9/22/2008 Autumn Equinox 15:44 U.T.
To understand what I am doing here, you must see the sun and moon as two separate bodies as they cross your sundial median line. The Sun is the standard body, because our earthly heat comes from this body, thus determining the seasons. When the exact midpoint between the two solstices comes, after the winter solstice, this mark shall determine the time when you "can" start the New Year. New Year comes at the first Rosh Chodesh either on or after this time, but never prior. To know for sure whether your calendar is one track or not, you can know by knowing this simple rule: the seventh month must always start on or anytime after the Autumn Equinox. If it starts before this, you are off and can end up sinning.
Likewise, by having this drawn out chart above, you will also know whether or not you will have a 13th month or "leap" month for the current year, depending where the monthly blocks land for any given year.
I hope this helps
Mare-ga'al Ben Yaakov
6/20/08 23:59 U.T. Summer
Where and when the sun is directly overhead
New Year 4/7/2008 = Biblical process