Among the considerable signs of showing gratitude to Allah are Zakah and charity. When a Muslim pays his Zakah or spends something in charity, his soul is purified from miserliness and he rises to the peaks of magnanimity and honor. This very act of spending money in charity and Zakah is a great sign of showing gratitude to Almighty Allah. Of course, all Muslims are commanded to show gratitude to Allah night and day.
In his explanation on this issue, Dr. Monzer Kahf, Scholar in Islamic Economics and Financial Expert, stated,
“A new Muslim starts the calculation of Zakah from the day she/he acquires Nisab (this is approximately US% 1500). If he has this amount on the day he became Muslim, so he is to begin counting the days from that day, and after 354 days he will have to see how much he has. If he has anything that is equal to Nisab or more, Zakah is due at the rate of 2.5% and every 354 days from then onward.
Nisab is the minimum amount that a Muslim must have before being obliged to pay zakah.
We are talking here about Zakah that is due on wealth, properties (except what is exempted, i.e. what is mainly personal, such as things related to residence, transportation and the like).
Regarding Zakah of agriculture, it is due on the day of harvest, while that of livestock has different Nisab although it begins the same way from the day one acquires Nisab.
In conclusion, if one owns wealth on the day he became Muslim and that wealth is equal to Nisab or more, then that is the first day for calculation.”