The thread starter is correct.
We need to pay zakat on things that we had in access once we pass one year on them, but if one is not very good with the calculations, then its safe to dospose the zakat on whatever assets and cash you hold that require Zakat, as mentioned by another poster above. This way you will also be paying zakat on whatever you had earned in the last year.
It is very important to keep the same cycle day in order to dispose the Zakat. If you decided to pay Zakat on 1st Ramadan, then stick to it and do it every year. The money that came in or went out even a day before would also be considered in calculating zakat.
Lets take an example on paying the zakat to make it more understandable.
E.g. Consider you have $100k in cash this current 1435 Hijri year on 1st ramadan, and also have $10k in form of other assets like gold, silver or any other asset. Now when 1st ramadan, 1436 hijri arrives, you find out that you earned in total of $20k in last year. The total you have in the cash is now, say $105k (because you spent $15k last year, and saved $5k), and say your gold stayed the same at $10k. If you decide to pay on whatever you have on 1st ramadan 1436, then you will be paying 2.5% on 105k +10k = 115k ($2875 zakat).
If you decide to calculate and pay zakat only on what you have saved for more than a year, then you will be paying 2.5% on original 100k + 10k gold = 110k ($2750 zakat).
This will also hold if you spent some of you saving as well from the last year. e.g you earned extra $20 this year, but spent $30k, then you will paying zakat on 120k-30k = 90k +10k = 100k ($2500 zakat).
Wal'laho Aalam (And Allah knows best)