The Rebbe's signature move with the calendar: the festivals are not fixed occasions but permanent instructions — "the Torah is not bounded by time." Every moed's light is drawn into the whole year (hora'ah nitzchis). The mournful seasons get a characteristic turn: grief is not the last word. The comfort is doubled — the future Temple will be greater than the first — and the days of mourning themselves will turn to festivals.
Thousands of his letters carry a seasonal blessing — that register is charted in the letters on blessings. What this thread isolates is the teaching: his standing move is to unfix the calendar. A festival is not spent, he holds, when its date passes; תורה אינה מוגבלת בזמן — its light is meant to be drawn into every ordinary day. And the sad seasons are not left in their sadness.
How the calendar is handled, by how often each move surfaces.
Note the rising line under "mournful days turn to joy" — heaviest in the 1960s–70s (60, then 48). As the correspondence widened, the reframing of grief became a larger part of what he wrote.
Two moves recur. He converts each festival's date into a year-round character — its light is to be carried into the ordinary days, not left on the page. And he refuses to let the mournful seasons stand in their grief: the comfort is doubled, the fast-days will become festivals, the month named for exile is blessed as the month of consolation. Here, verbatim.