A Holiday Calendar which can be of some reference to you can be found here.
It is synced from the Chabad.com website here.
Traditionally and generally, new months and in turn Jewish dates are calculated by sighting the new moon.
As there is no Sanhedrin, certified witnesses and the like to testify to the sighted new moon in Israel, the calendar was fixed by mathematics, long ago and agreed upon by the scribes and Pharisees (Matthew 23:1-3).
There are certainly those who seek to verify the actual sighted new moon either by third party, technology or with their own eyes, themselves.
One thing a person should perhaps note is that even independent eye witnesses trying to do what might seem a kind thing today, can still tend to vary on the dates that a new moon may have appeared on – amongst each other.
It is with this that the writer here, who is based outside of Israel, observes the Hillel 2 Calendar for Israel, the accepted calendar as per the halakhah here – which can be found here.
The calendar shown below is Chabad’s (may Hashem bless them in Messiah [Christ]) calendar for outside of Israel, and features things like Yom Tov (a type of double rest day for some holidays), a pharisaic tradition.