The fact that the corner of a building thrust toward the viewer looks shorter than an inside corner thrust away from the viewer can be accounted for by the

Müller-Lyer illusion

Explanation: It is a visual illusion in which 2 lines of equal length, have opposite shaped ends, in which the line that are feather tailed (i.e. lines extending outwards) appears longer than the one with arrow headed lines (i.e. lines going inwards.

in about winter like late november to january

answer; no longer than a reasonable period of time;