If you are below 400 health, and are affected by Guardian Angel, physical attacks which deal 0 damage will activate your Borrowed Time.

Same applies to Aphotic Shield and False Promise. When below 400 health, taking any damage during those activates Borrowed Time, even though they reduce the damage to 0.

Expected: Borrowed Time's passive activation should reach on damage after reductions, not before, so it doesn't get wasted while being immune to damage.

This would allow Abaddon to save his ulti while on low health by casting Aphotic Shield on self. Sometimes you just don't want it to activate when on low hp, but as of now there is no way to prevent it. Even worse is when the spell gets wasted simply because you were hit by damage while taunted by Winter's Curse, taking 0 damage. The curse easily wastes more than 80% of Borrowed Time's duration this way. Same goes for Guardian Angel when facing physical damage. Or Fate's Edict when facing magical damage. This works fine with spell immunity though.