When Does the Zakat Year Begin?
The zakat year begins on the date on which you were first in possessions of wealth above the nisab.Example: On Junaid's 18th birthday he is given a gift of £1000. This is the first time he has owned wealth over the nisab threshold, so his zakat year begins on his birthday. Junaid calculates the equivalent date according to the lunar calendar, and every year this date comes around, he calculates his zakat.
This will be your seed date, whenever it comes around you will have to calculate zakat, irrespective
of any fluctuations in the amount of wealth in your possession.
The only situation in which your seed date will change is if you were to become totally bankrupt and lose all your assets and belongings. In this situation, your new seed date will begin when you are once again in possession of wealth above the nisab.
If you are not sure of your seed date, then estimate it to the best of your ability.