Date palm (Phoenix dactylifera L.) is known for its social, environmental, and economic importance by many people in tropical and subtropical regions. Dates are an essential agricultural product in Iran and sometimes a staple food because of their high sugar content, vitamins, minerals, phenolic compounds, and antioxidants. This research aimed to explore the changes that occur in chemical compounds at different stages of fruit ripening. Five palm cultivars were comparable with each other in this regard. The fruits were harvested at various ripening stages (Hobabok, Kimri, Khalal, Rutab, and Tamar) from five date varieties, i.e., ‘Khenizi,’ ‘Mazafati,’ ‘Kaloteh,’ ‘Shahani,’ and ‘Mordasang.’ We measured phenolic compounds, anthocyanin, tannin, moisture, and total soluble solids (TSS) in the fruits at their different ripening stages. Average comparisons showed that the TSS content, anthocyanin, and phenol compounds increased during ripening. In contrast, antioxidant capacity, tannins, flavonoids, and moisture content decreased. Chemical compounds in the cultivars were different from one another at ripening. Thus, harvesting should take place according to the harvest purpose in each cultivar.