c#：如何获取特定时间段的前一年至今和前一个月至今？

DateTime today = DateTime.Today;
DateTime oneYearAgo = today.AddYears(-1);
TimeSpan timePeriod = today - oneYearAgo;

Console.WriteLine("从前一年的今天到今天共有 {0} 天", timePeriod.Days);

DateTime today = DateTime.Today;
DateTime oneMonthAgo = today.AddMonths(-1);
TimeSpan timePeriod = today - oneMonthAgo;

Console.WriteLine("从前一个月的今天到今天共有 {0} 天", timePeriod.Days);