We know at least two incidents where individuals experienced time dilation as per our scriptures - 1) King Kakudmi traveling to Brahma lok with his daughter Princess Revati 2) King Muchukunda fighting on the side of Devas against Asura
The third incident is indirect - Arjuna travel to Swarga lok before the war
However there seems to be another incident which takes place as per Uttara Kanda of Ramayana , where time dilation should have taken place. This was when Riksharaja took his new born sons Vali and Sugriva to Brahma lok after their birth. There Brahma consoled him and asked him to become king of vanaras at Kishkindha
Thereupon taking them, he came to the abode of Brahma. Beholding his son Riksharaja with Ins sons, Brahma, the grand-father of the celestials, consoled him in diverse ways. ......
......Brahma, having said this, the celestial emissary, with Riksharaja before him, proceeded to the highly picturesque city of Kishkinda. And having entered there with the velocity of the wind, he, at the command of the Patriarch, crowned the leading monkey Riksharaja as king;
It is clear from above that it was Riksharaja visiting Lord Brahma and not the other way around. From Princess Revati's example we know that 27 chatur yugas had elapsed when she was in Brahma Loka. But why don't we see something similar in Riksharaja's case ? Is it because Uttara Kanda of Ramayana is an interpolation ?