Tomorrow, 19th July, is the beginning of Moharram, an important day for Muslims, particularly Shias.
In this connection I may recount a recorded incident.
Once in the 1840s or 1850s Holi and Muharram fell coincidentally on the same day.
The then Nawab of Avadh, Wajid Ali Shah was a Shia.
https://en.wikipedia.org/wiki/Wajid_Ali_Shah
After taking out the tazia from the Bada Imambara and burying it in the Karbala in Lucknow, he enquired why Holi was not being celebrated.
He was told that since Holi was a festival of joy, while Muharram was an occasion of sorrow, the Hindus of Avadh had decided not to celebrate Holi that year, out of respect for the sentiments of their Muslim brethren.
On hearing this the Nawab declared that since Hindus had respected the sentiments of their Muslim brethren, it was the duty of Muslims also to respect the sentiments of their Hindu brethren. He then announced that Holi would be celebrated the same day throughout Avadh, and he himself was the first to play Holi, and it was played throughout Avadh that day ( even by Muslims ), although it was also Muharram day.