Sundial doesn't stop weapons, that's why your gavel in the weapon slow dealt a full 7 damage. It
does, however, stop momentum creatures. Normally.
Flying Fahrenhiet and Gavel are the only exceptions to this rule, as they have damage that adds onto their regular attack, but does not show up on the card.
Presumably only Zanz knows why this is so, because Sundial is supposed to make creatures skip the attack phase of their "Turn". It might be because they have a different code than other creatures used when they attack, that, instead of attacking during the part of their turn when other creatures would, they add +1 (Or +X/5, where X=
) to their damage, which remains unaffected by the Sundial "Turn" skip.