If it feels like daylight saving time lasts longer than it used to, well, it does. Why do we change clocks at all, and why does daylight saving time now span nearly eight months of the year? Daylight saving time in theory is about saving energy, along with promoting social benefits. Daylight saving time continued this way for 20 years, until Congress amended the previous law to extend DST. From 1987-2006, daylight saving time ran from the first Sunday in April through the last Sunday in October.