The official spelling is Daylight Saving Time, not Daylight SavingS Time.
Saving is used here as a verbal adjective (a participle). It modifies time and tells us more about its nature; namely, that it is characterized by the activity of saving daylight. It is a saving daylight kind of time. Because of this, it would be more accurate to refer to DST as daylight-saving time. Similar examples would be a mind-expanding book or a man-eating tiger.Saving is used in the same way as saving a ball game, rather than as a savings account.
Nevertheless, many people feel the word savings flows more mellifluously off the tongue. Daylight Savings Time is also in common usage, and can be found in most dictionaries.
Adding to the confusion is that the phrase Daylight Saving Time is innaccurate, since no daylight is actually being saved. Daylight Shifting Time would be better, but is not as politically desirable.