Cluny
For this year’s calendar of the Eastern US Eparchy of St. Thomas, the Feast of the Presentation (known more commonly among Chaldeans as Shimoun Sawa, meaning, Simeon the Aged/Old) will be celebrated on the First Sunday of February. Sundays are non-fasting days. The Supplication or Fast of the Ninevites will be the next three days on Feb. 2, 3, and 4.
However, for this year’s calendar of the the Western US Eparchy of St. Peter, the Feast of the Presentation was already celebrated on January 1st. They will start the Fast of the Ninevites on Feb. 2, 3, and 4.
I’m not certain as to the explanation for why the discrepancy between the two Assyrian-Chaldean Catholic Eparchies on the Feast of the Presentation. In any case, the feast does not fall on the fasting days.
Now, as you mentioned, when you look at the Roman Catholic calendar, as well as, the Byzantine Catholic Church in America calendar, the Feast of the Presentation will be on Feb. 2. What this means is that while Latins and Byzantines will be feasting on this day, the Assyro-Chaldeans will be fasting.

It’s no problem, a mere difference in liturgical custom.
God bless,
Rony