What is entailed by breaking the fast for some days in Ramadan four years ago due to strenuous work under the sun, given that the number of days is not remembered, and are there any rights of Allah entailed by that?

If a person cannot perform his strenuous work except by breaking his fast, and he is compelled to work, then it is permissible for him to break his fast. However, he must intend to fast at night and then break his fast only when necessary. He must make up for the days he missed fasting, and feed a poor person for each day if he delays making them up without a valid excuse. If he does not remember the number of days, he should investigate and make up what he most likely believes will clear his conscience, or what he is certain will clear his conscience, as this is more cautious. He must repent to Allah if he broke his fast without necessity.