Ideas
In regards to 30 Adar I which is the first day of Rosh Chodesh Adar II, Reingold & Dershowitz hold that the birthday in a non leap year will be on 1 Nisan. However many halachic authorities hold by 30 Shvat since it is the first day Rosh Chodesh Adar R&D don't state what their reasoning is but logically all dates are always the number of days after the first of the month. The 30th of Heshvan Kislev and Adar I are always 30 days after Rosh hodesh which are 1 Kislev 1 Tevet when 30 does not exist and 1 Nisan which is 30 days after Adar when Adar I doesn't exist.
You should celebrate your birthday every year!
Hebcal uses the anniversary algorithm defined in Calendrical Calculations by Edward M. Reingold and Nachum Dershowitz, which accords with Ashkenazic practice. Reingold and Dershowitz write:
Someone born on the thirtieth day of Marcheshvan, Kislev, or Adar I has his birthday postponed until the first of the following month in years where that day does not occur. [Calendrical Calculations p. 111]
In other words, on years where there is no 30th of Kislev, your birthday is celebrated on the 1st of Tevet.
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You should celebrate your birthday every year!
Hebcal uses the anniversary algorithm defined in Calendrical Calculations by Edward M. Reingold and Nachum Dershowitz, which accords with Ashkenazic practice. Reingold and Dershowitz write:
In other words, on years where there is no 30th of Kislev, your birthday is celebrated on the 1st of Tevet.