You are not alone in the calendar challenge thing. I am not numerically challenged and am a bit of a science geek (love strata - find it fascinating) but cannot for the life of me keep up on basic things like appointments and deadlines.
Somehow everything takes me by surprise a few hours before it is supposed to happen.
I have a long list of tricks I try on myself and routines I fail to adopt to help with this. Some work better than others but I think it is how we perceive time that is the problem (I think it has benefits too).
All to say I totally feel your pain on the deadlines and like all deadlines and other bad things, this too shall pass.