Hi there,
Where are you applying?
If you're applying in the US I would get moving ASAP - demand is through the roof. If it's Europe, wait another couple of months. Notice a pattern? "Follow" covid vaccinations/economic recoveries.
Furthermore, you need to network. I prefer the strategy of applying if/when you have a referral or have exhausted all networking avenues. Far more important than specific timing is having an "in" at the company.
Finally, if you're wondering about specific cohorts/recruiting cycles, it really does depend on the office...so, you may as well network, reach out to HR, etc. to figure out when these are for your particular officde!