The Gurbani refers to several months of the Bikrami calendar and associates them with seasons. Unfortunately, the Bikrami calendar, unlike the Common Era calendar used throughout the world, is not attuned to seasons and with the passage of time aberrations are bound to mount. The year used as basis for the Bikrami calendar differs from the tropical year, which is attuned to seasons and is used as a basis by the Nanakshahi calendar and the Common Era calendar. In the Gurbani month of Poh has been described as one of cold weather but with time, this month instead of overlapping with January [December-January] will shift to February and then to March. The Bikrami calendar then will no longer be true to Gurbani.
Seasonal festivals have also shifted over a long period of time and will continue shifting. For example, Lohri in 532 A.D. was on December 18 and Maghi on Dec. 19 but now they fall in the middle of January. In another 2000 years, these will occur in the middle of February and their association with the winter season will no longer exist.