Traditionally, network updates are implemented at a certain block number, not by date/time.
A date/time when an update is expected to occur can be estimated by calculating the time between the current block and the execution block using current block production times. The block production time fluctuates slightly depending on a number of factors, meaning any estimated time will also fluctuate.
The update named Arrow Glacier implemented in December 2021 pushed back the Ice Age / Difficulty Bomb to a block estimated to be seen in June 2022.
The rationale for that delay was published by Tim Beiko
‘The following script predicts a ~0.1-second delay to block time by June 2022 and a ~0.5-second delay by July 2022. This gives reason to address because the effect will be seen, but not so much urgency we don’t have space to work around if needed.’