How Is 17 Tammuz Relevant Today

The 17th of Tammuz is the tragic start to the Three Weeks, a period of intense mourning that culminates with Tisha B'av – the day the Temple was destroyed. And if that's not enough, the Mishna lists even more calamities that took place on the 17th of Tammuz. Is it just a coincidence that all these terrible moments happened on the same day? Is the 17th of Tammuz just the Israelites’ bad luck day, or is there a common theme that runs throughout the events of this day?