This phrase is often attributed to St. Augustine: "Trust the past to God's mercy, the present to God's love, and the future to God's providence."
Here's the scoop. I simply cannot find any direct match for this quote in Latin, in Augustine or elsewhere. The earliest date that I could find for the use of the English version is 1906 ("The Manual of the Holy Catholic Church" by James McGovern). The quote has no attribution there, but it is followed by a quote from St. Augustine! The vast majority of French versions are unattributed. Interestingly, François de Sales is quoted as the originator of this particular phrase: "il faut abandonner le passé à la miséricorde de Dieu, le présent à notre fidélité, l'avenir à la Divine Providence." Note how the middle is changed from God's love to our faithfulness. This would seem to indicate that de Sales knew a similar quote and simply modified it. Unfortunately, I cannot find his French quote in a complete French edition and there is no Latin edition available. Also, in 19th century French texts there is a phrase that only contains references to past and future. Nothing too interesting came out of my research on the Italian and German versions of the phrase.
It looks as if at some point a rather commonplace phrase was ascribed to Augustine, or perhaps someone felt that it expressed his understanding of the nature of things. It is well known, after all, that Augustine was very much interested in the philosophical complexity of time. But just like Tertullian never actually said, "Credo quia absudrum." I think, we have a modern-day Pseudo-Augustine quote!
See also Bible verses in Latin