Another persistent timing problem stems from the differences in holiday and academic calendars. As noted earlier, students from over $160$ universities in $50$ countries take part in X$-$Culture every semester, and all these universities and countries have different academic and holiday calendars. The different dates for the semester start and end make it difficult to find a common time window when the classes at these different universities are in session. As a result, the project start must be delayed until the date when the semester starts at the "last" university and finish the project when the "first" university ends its academic session, which necessarily shortens the duration of the project.