We have the word "eternal" that refers to something that will exist forever, something that never ends, which is related to the word "eternity" that refers to the end of time.
Is there a similar word for "the beginning of time", or something that has existed, as some might say, "since forever"? As an adjective, it would be used like: "My love for you is ...". The noun could be used like: "I have loved you since ...".
There is such a Persian word, for example, widely used in Persian literature, which is usually used to describe God, Love, etc.