Nope. The actual wording under 18 U.S.C. § 922(g)(1):
You need to read the definitions included in the statute.
18 USC 921(a)(20) reads:
(20) The term “crime punishable by imprisonment for a term exceeding one year” does not include—
(A) any Federal or State offenses pertaining to antitrust violations, unfair trade practices, restraints of trade, or other similar offenses relating to the regulation of business practices, or
(B) any State offense classified by the laws of the State as a misdemeanor and punishable by a term of imprisonment of two years or less.
What constitutes a conviction of such a crime shall be determined in accordance with the law of the jurisdiction in which the proceedings were held. Any conviction which has been expunged, or set aside or for which a person has been pardoned or has had civil rights restored shall not be considered a conviction for purposes of this chapter, unless such pardon, expungement, or restoration of civil rights expressly provides that the person may not ship, transport, possess, or receive firearms.
So yes misdemeanors punishable by two years or less are excluded.
Also my comments on ex post facto were mostly related to lautenberg.
You can't change the maximum punishment for an offense after the fact but you can change the definition of a qualifying crime and prohibit future conduct.
The poster was comparing this situation to lautenberg and it is different.
If convicted of an offense punishable by 6 months in prison and then three years later the state changes the maximum punishment to 3 years in prison you were still convicted of a crime punishable by less than a year.