FIDE and US update questions

When in the month does the US top 100 lists get updated?

When in the month do the FIDE ratings get updated?

for FIDE it's the first day of every month (eg. you increase 100 pts in March and your rating 1400, then it will change to 1500 on the 1st of April)

According to the USCF website, "Official ratings lists are generated on the 3rd Wednesday of each month and become official on the 1st day of the next month."