@private
t1 <= t2, where nil is treated as “distant future”
# File lib/util/schedule.rb, line 23 def before_eq(t1, t2) (t1 && t2) ? (t1 <= t2) : t1; end
min(t1, t2) where nil is treated as “distant future”
# File lib/util/schedule.rb, line 26 def earliest(t1, t2) before_eq(t1, t2) ? t1 : t2; end