Calendars work on a weekly or monthly rotation. Your Calendar rewards are based on your progression level at the start of the current Calendar cycle. So, even if you level up mid-cycle, you will need to wait until the next cycle begins to receive the higher-progression rewards.
For example: If you are at Thronebreaker when a Calendar cycle begins and then reach Paragon during that cycle, your calendar will continue to provide Thronebreaker rewards until the next cycle.
You will have access to the new tier of rewards when the current Calendar cycle concludes. Keep pushing forward and enjoy the benefits of your new level when the next cycle begins!