In Jain tradition, the Panch Kalyanaks of the 24 Tirthankaras are remembered as five auspicious life events: Garbha, Janma, Diksha, Kevalgyan, and Nirvana. However, there is no single universally fixed Gregorian date for all 24 Tirthankaras’ Panch Kalyanaks. Their observance is traditionally tied to the Jain lunar calendar (tithi) and can vary by sect and calendar tradition. ( jainknowledge.com)

So, instead of one fixed date for all 24, Jain tradition usually records them by tithi and sacred place. For example, the sources note these well-known dates for Lord Mahavira: Janma Kalyanak on Chaitra Shukla Trayodashi, Diksha Kalyanak on Vaishakh Krishna Dashami, Kevalgyan on Vaishakh Shukla Dashami, and Nirvana on Kartik Krishna Amavasya. They also note Parshvanath’s Janma Kalyanak on Paush Krishna Dashami. ( jainknowledge.com)

Because the full Panch Kalyanak date set for all 24 Tirthankaras is not presented as one fixed universal list in the source, the most authentic Jain answer is: their dates are traditionally preserved in Jain panchangs and scriptures, not as one common Gregorian table for every Tirthankara. ( jainknowledge.com)

If you want, I can next provide a traditional tithi-wise list of the Panch Kalyanaks for the 24 Tirthankaras in Jain format.