Athens over Easter?

Regarding sites and museums:

On April 18th (Good Friday) and Saturday 19th, there may be restricted or modified opening hours.

On Easter Sunday most sites and museums will be closed.

On Monday 21st most sites and museums will be open according to their usual hours

Are you referring to Easter as in the US or Greek Easter which is several weeks different from the US?
Easter is the most important holiday in Greece so make sure the dates you are looking at are taking Greek Easter into account.

It happens every few years but next year, the date for our Easter and Greek Orthodix Easter falls on the same day, April 20. I was very lucky to spend Greek Easter in Athens in 2022. While museums are closed that day, restaurants and shops are open. In fact, you will see lamb being roasted over a pit all over Athens that weekend. If you do go, try to go to a Greek Ortodox church at midnight on Easter eve. Everyone waits outside holding unlit candles waiting for the priest to come out of the church. The priest comes out and says a few prayers while everybody lights their candle from a candle brought out from the church. You will see the candlelight spread through the crowd. Then they celebrate with fireworks. To our disappointment, we didn’t see fireworks but the ceremony was very touching.

If you get a chance to go to a midnight mass, GO, it is an amazing experience.
Easter in Athens is magical!

Thanks all for your input!

It is my understanding that many Athenians go back to other parts of Greece either islands or mainland where their families came from or still have relatives to celebrate Greek Easter there so it may be "quieter" in Athens than normal.