I remembered reading about kneeling in church, but I don't remember where. I seemed to recall that kneeling, for whatever reason, is frowned upon by some and not by others. I respectfully ask- what's the deal? Our parish, OCA, had a kneeling service during Pentecost.
Canon 20 of the Council of Nicea has this to say:
Seeing that certain people kneel on Sunday and during the Pentecost (Paschaltide) season, so that there might be the same practice in all the communities, it has been decided by the holy council that prayers should be addressed to the Lord standing up.
This rule was reiterated in Canon 90 of Trullo:
We have received it canonically from our God-bearing Fathers not to bend the knee on Sundays when honoring the Resurrection of Christ, since this observation may not be clear to some of us, we are making it plain to the faithful, so that after the entrance of those in holy orders into the sacrificial altar on the evening of the Saturday in question, let none of them bend a knee until the evening of the following Sunday, when, after the entrance during the Lychnic, again bending knees, we thus begin offering our prayers to the Lord. For inasmuch as we hare received it that the night succeeding Saturday was the precursor of our Savior’s rising, we commence our hymns at this point spiritually, ending the festival by passing out of darkness into light, in order that we may hence celebrate en masse the Resurrection for a whole day and a whole night.
Not all the local churches follow this rule with the same strictness, and I'm aware that even priests violate this rule at one point in the Sunday Liturgy, but no kneeling on Sundays and during the fifty days between Pascha and Pentecost is the universal rule.
The kneeling service of Pentecost is a Vespers service that, according to strict practice impractical for most parishes, is to be performed on Sunday evening. As such, this service technically belongs to the day (Monday) AFTER Pentecost
, even if it is performed immediately after the Sunday Liturgy as in many parishes. (Kneeling on any day but Sunday, and then outside of the Paschal season, is always permitted and often expected.)