Hello! It looks like you are asking about the poem named "Rakhi, For Aradhana" by Vikram Seth.
This poem was written by Vikram Seth for his sister, Aradhana. Here, Rakhi refers to the Hindu religious festival, Raksha Bandhan, which celebrates the bond between brothers and sisters. The word Raksha means protection, while the word Bandhan means to tie or to bond. During the festival, sisters traditionally tie a bond made of red and gold threads around the wrist of their brothers to celebrate their relationship. As the Rakhi is tied, a prayer is often offered for the happiness and prosperity of the siblings. Brothers pledge to protect and honor their sisters all the rest of their lives, and sisters pray for long life and prosperity for their brothers. The sister puts a sweet into her brother's mouth and he reciprocates by presenting her with a small monetary gift of appreciation.
This poem starts with Vikram telling his sister that he has forgotten the time of year her Rakhi was delivered to him. However, he states that no matter what time of year he received the Rakhi, some things will never change. They stay the same. After all, the Rakhi was a contract of trust between the siblings; Vikram tells Aradhana that he knows that it was a contract made with more parties than just the two of them. (Rabindranath Tagore is credited with popularizing the Rakhi festival for the purposes of societal unity. Sometimes a mother, daughter, or sister will tie the Rakhi around the wrist of a male relative.)
He places the Rakhi across his right wrist and struggles to tie it on with his left hand. He laments that he has forgotten half the sacred rites and that she should have been the one to do the honors instead of him. He promises her that he will give her his gift in '78. He says that the numeral representation of this future date of their meeting looks curious; he tells her not to be surprised if they meet as strangers when they next see each other. However changed both of them are, he is thankful that the customs will stay the same, bringing from the past the undying days of settled traditions they have come to depend upon.