Vedanta tells us that Time is relative. We experience constantly, as when we are enjoying ourselves we feel "time passes quickly." When we are bored we find time can "stand still". Objectively, we see this in the use of calendar systems, about 40 of which are presently in use throughout the world today, primarily for determining the dates of religious celebrations within the various.
The present day Gregorian Calendar was established by Pope Gregory in 1582. It replaced the Julian Calendar, which was in use by the Roman Empire at the time of Jesus' Birth, established by Julius Ceasar in 45 BCE. (Prior to this, yearly calendar making within the Empire was exploited, with months being added or deleted in order to keep favored politicians in office.)
Orthodox Christianity still uses the Julian Calendar to determine its observance of Christian holy days. (I'm invited to Christmas service this Friday.)
Kalpataru Day took place on New Year's Day according to the Gregorian calendar, which is in general use throughout the world. Followers of Vedanta according to the Ramakkrishna tradition feel that Sri Ramakrishna's blessings bestowed on this day transforms New Year's Day into a special day with Holy significance.
That Swami Vivekananda chose July 4th to leave the body gives this American holiday holy significance too. He had written a peom "To the Fourth of July", so knew the historical meaning of the day.
