Tisha B'av 2018 falls out at nightfall on July 21, and concludes at nightfall on Sunday, July 22.

The fast of Tisha b'Av falls on the Hebrew calendar date of 9 Av. Here are the coinciding secular dates for the upcoming years:

2019:   August 10-11
2020:   July 29-30
2021:   July 17-18

Note: The Jewish calendar date begins at sundown of the night beforehand. Thus the fast begins with sunset of the first secular date listed, and concludes at nightfall the following day.

See Also

When is Rosh Hashanah in 2018, 2019, 2020, and 2021?
When is Yom Kippur in 2018, 2019, 2020, and 2021?
When is Sukkot in 2018, 2019, 2020, and 2021?
When is Shemini Atzeret / Simchat Torah in 2018, 2019, 2020, and 2021?
When is Chanukah in 2018, 2019, 2020, and 2021?
When is Purim in 2018, 2019, 2020, and 2021?
When is Passover in 2018, 2019, 2020, and 2021?
When is Shavuot in 2018, 2019, 2020, and 2021?