Calculating zakaat

Q:

1. When must I pay my zakaat? Is it during a specific month or at any time?
2. When working out my zakaat, do I only consider the gold/silver and cash that I have at that specific time or does it work in cycles?

Q: In the country I stay, there is a big difference in the black dollar and official dollar rate. The dollar in this country is not the local currency. When I change dollars, I change on the black market because of the rate being higher. I normally take out my zakaat in the local currency. On the dollars that I have, should I take out my zakaat on the black market rate or on the official rate?

Q: My father owned an apartment in Pakistan which had always been on rent. A week back, he sold it and received the money against it two days ago. My question is, when giving zakaat, will this money be taken into account? Or will it be considered after it has been in possession for a year?

Q: I have always had my Zakaat anniversary as the 15 of Ramadaan. If I wish to change this date is it possible? Let's say I wish to from next year change my year to 15 Shabaan. I will do all my calculation on that date and give Zakaat at 2.5%. Is this possible? Alternatively, if the date I wish to use in future is 15 Shawaal, how would I put this into effect? Bearing in mind that this will then make it a 13 month year.

Q:  I have a monthly income of R10 000 which is paid on the 1st of every month. At the end of the month I barely have anything left. I also have no savings. I was previously wealthy and also I never went insolvent. I always took out my zakaat in the first week of Ramadhan. If the first week of Ramadhan falls on the 1st week of the gregorian calender when I receive my salary, is zakaat waajib on me?

Q: Some years ago, there were some riots in a certain place. The valuables from the house were placed elsewhere. Some were taken to the business, which was a big wholesale, for safekeeping and placed in a remote part of the safe. Included in these valuables which were taken to the business was some jewellery which originally belonged to the mother who has since passed away. This jewellery has now been found after many years in which it was regarded as lost. There are two questions:

1. Is there Zakaat on this jewellery for the previous years?
2. The mother had left a note with the jewellery stating that it should be given to her youngest son who was 9 years old at the time. Is this gift valid?

Q: Someone let another borrow money. Is zakat to be payed on that amount of money that he let another borrow at the end of each year? or is it due after the money is returned to him?

Q: On what is the zakaat nisaab worked out on?

Q: My father died without giving the meher money to my mother. After my father's death my mother will get the meher money from his property. Then is it necessary to give zakat on that money calculated from the day of marriage or from the day my father died or the day my mother receives the money?

Q: In South Africa, Government taxes can amout to 40% of ones income. If any, how does this affect our annual zakaat?