We can never be "safe to say." Humans often do things that are unexpected. Pilgrims traveling to Jerusalem from Galilee for Passover routinely purchased their lambs upon arriving in the city rather than herding them along on the three-day journey.
While it was permitted to bring a personal lamb, doing so was impractical. The journey from Galilee to Jerusalem took several days, and the animal had to remain in pristine, unblemished condition to be accepted for Temple sacrifice. Transporting a sheep over rough terrain increased the risk of injury, which would disqualify it.To solve this problem, a massive market for Passover lambs was established in Jerusalem. The Temple authorities oversaw the inspection of animals to ensure they met all strict Levitical requirements. Because of this, most pilgrims, including Jesus and his disciples, arranged to buy their approved, ready-to-sacrifice lambs in the city just days before the Passover. Remember Jews from all over the western world came to Jerusalem for the major feasts, few could have brought unblemished lambs if those certifying and selling their own lambs had anything to say about it.
As to the calendar, for events within the Galilee their unique calendar was sufficient for their day to day needs. Once going to Jerusalem the Temple calendar rules applied. "When in Rome......"