-- Calendar arithmetic builtins: add-mo, last-dom, next-business-day, day-of-week.
-- run: demo
-- out: 1709164800
-- add-mo dt:n n:n > n — add N calendar months, snapping end-of-month.
-- last-dom dt:n > n — epoch of last day of month at 00:00 UTC.
-- next-business-day dt:n > n — next weekday (skip Sat/Sun).
-- day-of-week dt:n > n — 0=Sun 1=Mon 2=Tue 3=Wed 4=Thu 5=Fri 6=Sat.
-- 2024-01-31 00:00 UTC = 1706659200
-- Jan 31 2024 + 1 month = Feb 29 2024 (leap year snap) = 1709164800
demo > n
add-mo 1706659200 1