It is really interesting for you to know that Iranian use 4 calendars to find a date. As there are many occasions and events in Iran and because Iran is a multi cultural country, people have to check the events with different calendars.
Persian New Year is shown in our own solar calendar. It is based on earth's rotation and is the most exact calendar in the world.
Ancient Calendar is another one which was made many many years ago and our ancestors used to use it. Although it has changed a lot, people refer to it when they want to see the original name of the months or some old celebration.
We also follow a lunar calendar which is made by Arabs. As we are Muslims, we should follow it for our religious events like Ramadan, Martyrdom of our religious Leaders and Prophet.
Iranian use the Christian calendar as well. For some interesting events like Valentine's day and Christmas they have a look at their Christian calendar too.
That is why you see at least 3 numbers for each date in our calendar. For example, our calendar shows 1st Farvardi, 21st March, 3rd Rajab. The first one is from solar, the second from Christian and the last is from lunar one. The Ancient one is also the same as 1st Farvardin.
As Iran is full of cultural attractions and events and because we are aware you are eager to get involved with our culture, let's see which Iranian is waiting for you and what cultural attraction you are going to experience.