Our Gemara on amud aleph discusses the obligation to announce a lost object to alert the owner. One opinion is that it should be through the entire annual cycle of all three Jewish holidays, Pesach, Shavuous and Succos. Presumably, since people make pilgrimages to Eretz Yisrael at least once a year, this will allow for sufficient interaction that hopefully the person who lost the object will be notified.
Akeidas Yitschok (69) discusses this phenomenon and ties it into an appreciation for Judaism’s respect for time and cycles. The weekly cycle of Shabbos is reflective of a physical and spiritual pattern of work and then reflection, which expands to the seven year Shemitta cycle, and 7 x7 Yovel cycle, and even the human lifespan (Tehillim 90:1) of 70-80 years. He further draws comparison to the idea of taking 12 months to despair on a lost object to the twelve months that it takes to grieve a death or to assist a deceased in achieving forgiveness (Semachos chapter 14.) When one goes through an entire year, each season, each day, reminds and brings up various aspects of experience and reflection. This causes a person to recall various states of mind and process them. Even the Niddah cycle forces each couple to confront the biological clock. This is not only about having children. It also stops sexual activity and intimacy to allow for reflection, assessment and a reset regarding the state of the emotional and physical union.
In both trauma treatment and in psychological development theory, there is an awareness that anniversaries can be powerful. They arouse old feelings and can cause distress but also be opportunities for repair. Time may heal many wounds, but without conscious awareness of time and appropriate reflection, the benefit of time is less effective. Judaism’s strength is providing mindfulness and opportunities to reflect on life and self through annual cycles and rituals.
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
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