"Tomorrow is another day. Not just any day. But it is a day, it will get here. There's no question." Reggie Watts
"Behold, Thou hast made my days as an handbreadth; and mine age is as nothing before Thee: verily every man at his best state is altogether vanity." (Psalm 39:5)
To intercalate means to put another day into the rotation (see the "cal" in there? Same root.). To add something but specifically with reference to a calendar cycle. As we pretty much all live by the same calendar, I don't think we see this connotation as we would, say several thousand years ago were we tasked with creating and enumerating "the calendar" for the masses and expected to use the word in a sentence, correctly. Here's another one from school: "One day, I went to school and the teacher told me to use the word intercalate in a sentence." To intercalate intercalate into a sentence, as it were. But neither count, say, when you have reached your last day and you're hard-pressed to (impossibly) add another day to your rapidly declining allotment.
"So teach us to number our days, that we may apply our hearts unto wisdom." (Psalm 90:12)
"Verily, verily, I say unto you, The hour is coming, and now is..." (John 5:25)
When I was a kid, I made a promise to myself that I'd use every June twenty-first to play outside as late as possible. But it wasn't until I got older that I realized this fact: With the beginning of Summer, the days begin to shorten. It's this way with other realms of life as well. When you reach the peak, you begin to descend, to nadir (I don't think I can verb that word). This is my point: God has a program. If you're a Christian and you desire to walk in it, then you're part of it. I'm not going to get into hard theology or philosophy by outlining the various types of will and doctrines of election, etc. I am going to say, that as time flows, things change. And with each season you walk in (they have their own feel), God has something He wants to do for you, to show you, to give you, and to use you to do for Him in your world. Even as you wander around on this earth and essentially "play outside" like a (His) child.
"And Jesus called a little child unto Him, and set him in the midst of them, And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the Kingdom of Heaven." (Matthew 18:2-3)