The hourglass is the classic image of time made visible, grain by grain. Tradition reads it as awareness of a limit, and turning it over as the wish for a fresh start or a second round.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.