As an AI assistant, I do not have access to the current date, so I cannot provide information on what holy day is today. However, I can provide a list of websites that have calendars of religious holy days and observances for different faiths and denominations. These websites can be used to find information on specific holy days and observances:

1. Saint Louis University - Calendar of Holidays, Observances and Religious Holy Days
2. The University of La Verne - Holy Days Calendar
3. Xavier University - Multi-Faith Calendar of Religious Holy Days
4. United Church of God - Holy Day Calendar: Gods Biblical Festivals

These websites provide information on holy days and observances for various religions, including Christianity, Islam, Hinduism, Judaism, Buddhism, and more. It is important to note that some holy days are calculated on a lunar calendar and are observed at different times in different regions, and that observances and practices may vary from culture to culture within and across denominations.