you should wait until the soil and the forecasts indicate it is time...

it is not really a calender thing ...

check my answer at the link .... for good clues

in my z5 .. last frost date is around MAY 25th ... you can plant no TENDER annuals until near that time ...

they will frost or freeze to death ...

seeds require a certain soil temp ... and they will not germinate until the soil is that temp .... probably around 5/1 ... and they will need to be protected from the frost freeze also ...

just because a phase of the moon.. indicates on the calender.. that it is technically spring ... there are many variables you need to consider.. before assuming.. it really is spring.. in a garden sense ..

all that said... experiment ... keep notes... if you have a package of seeds.. plant 1/4 now.. 1/4 in two weeks... etc ... and figure out how it all works in your garden.. in your soil.. in your zone ...

good luck .. gotta run... ken

Here is a link that might be useful: link