Track your days in Monaco during the calendar year. Staying in Monaco for more than 183 days per year (184+ days) is one basis used for Monaco residence certification for tax formalities. Other criteria may also establish residence, including having your principal centre of activities in Monaco, spending your longest annual stay there, or, failing those tests, having your home there. This tracker only monitors the day-count test and does not by itself determine tax residence. Special rules generally apply to French nationals.
https://journaldemonaco.gouv.mc/fr/Journaux/2020/Journal-8515/Ordonnance-Souveraine-n-8.372-du-26-novembre-2020-portant-modification-de-l-Ordonnance-Souveraine-n-8.566-du-28-mars-1986-relative-au-certificat-de-residence