Here is some reference information about Huaquechula, When does the feast of the Holy Cross in Huaquechula start?

One major festival is that of the Feast of the Holy Cross, which dates back far into the colonial period. It has a community cross made from basalt called the “Cruz de Huaquechula” which is incrusted with various relics related to the original cross of Christ. It is said to be so heavy that it cannot be lifted unless the bearers pray and the church plays a special melody on its bells. The festival lasts nine days beginning in April ending on May 3, with mass, traditional dance, food and music played by bands playing wind instruments, and fireworks set off from large frames in the shape bulls. The event has been named part of the Cultural Heritage of Puebla. During this event, traditional festive wear such as that of the charro and the China Poblana can be seen.[4][1]

April 25th.  It ends on May 3rd, and lasts 9 days.