Four Calendar Laws:
1) The New Moon nearest the start of spring (time of Vernal Equinox) is always Abib.
2) The New Moon is defined as a Dark Moon, starting from the sunset that follows lunar conjunction.
3) Keep Shabbat where you live but Feasts on Jerusalem Standard Time.*
4) The Omer count begins on the 16th of Abib, ends on Shavuot 50 days later and can hit any day of the week.
Expanded in detail in this pdf:
– Andrew Gabriel Roth, Wheel of Stars.
Shareable link to this page:
* Once the Feast has arrived according to JST, start the feast when the sunset arrives where you are for that JST day of the month. As for weekly Shabbats, they begin where you live when the local sunset ends the sixth day of the week.