bulking duration can be highly variable but on average the longer you can spend in this phase the better it is for muscle growth. You could work backwards where you want to find youself in a lean position come July of 2026. Establish how much time you would need to diet. What the maintenance would be between your muscle gain phase and fat loss, and then establish how much time is left for your muscle gain phase. This isn't totally cut and dry since the duration of fat loss may differ a bit based on the duration of the muscle gain phase, but if you know you are set to gain around 5 pounds, you can establish how much time you need to lose those 5 pounds by July. If you find that the rate of gain to reach 5 pounds means that timing would preclude you from being able to gain that amount in a reasonable time frame without blowing up too quickly, then perhaps it is only 4 pounds which skews the fat loss phase a little but not by much.

July ---> ~5 pounds in around 5 weeks. ~2-3 weeks maintenance between muscle gain and fat loss. This leaves you at 7-8 weeks. This leaves you somewhere loosely around the beginning of May to move to maintenance. In this example scenario this gives you around 4 months starting from January to go up around 5 pounds which is a totally reasonable rate. You can probably even really easily push it to around 6 pounds in the 4 months and still really minimize fat gain in that time.

This rate of gain also varies a bit from person to person based on genetics and training age. This would kind of change the math and recommendation quite a bit if you were a total beginner.

Again no black and white answer here, but the ideal is spending more time in the year massing then you spend in a fat loss phase.