What must I pay from my zakat money this year and when, taking into account the dates the nisab for gold and silver was reached and the actual dates for paying zakat?

If a layperson acts upon a valid opinion, believing it to be the correct one, then they have fulfilled their obligation. They are not required to undo their initial action if they subsequently come to believe another opinion is more sound, because "Ijtihad (definition) (independent reasoning) is not invalidated by another Ijtihad."

Therefore, there is no blame on the questioner for having relied solely on the value of gold to estimate the nisab (definition) of paper currency in the past, as this is an opinion held by some scholars.

However, the preponderant view in recent fatwas, and the resolution of the Islamic Fiqh Academy, is that the nisab for paper currency is determined by the value of the lower of the two nisabs, either gold or silver.

If the questioner wishes to exercise caution and adopt the more scrupulous approach, they should advance the date of paying zakat (definition) to align with the possession of the nisab of silver. This means advancing it by eight lunar months (the difference between the date of possessing the nisab of silver and gold). So, if they paid the zakat for this year last Safar, they should consider it for a past year. They should then prepare to pay it next Rajab for this current year (1437 AH). By doing so, they will have paid zakat on their wealth four times for four years.