Sometimes it happens where a person accepts Christ as their Saviour and before they can be baptized, they die. When we come together to take of the Lord's supper, it isn't a time for your next meal and a time to be laughing or being merry. We are to humbly come in reverence. Jesus that same night in which he was betrayed took bread. There wasn't a day or a time given for us to observe communion but there were many warnings given to show the penalty of taking it unworthily in verses 27-30.
Some churches observe communion once a month, some every two weeks others once a week.
Each church decides when according to their doctrine and what they believe as to when it should be observed. One thing we know, is that what Jesus offered to the disciples was not His actual blood and body, because He was still with them and had not been crucified yet. The Old Testament teaches us at that time it was unclean to even touch a dead body. There was a New Testament to be written, a new way for our sins to be forgiven. Through the shedding of the blood of Jesus Christ.