Windows has no Bikram Sambat awareness. NepDate Widget is a free WPF desktop app that fills this gap with a live BS date in the taskbar, a full calendar with Tithi and holidays, Preeti-to-Unicode conversion, a keyboard launcher, local image processing, and a network toolkit.
AddDays, AddMonths, AddYears, and NepaliDateRange - the complete date arithmetic and interval API in NepDate. Covers the awayFromMonthEnd overflow policy, fiscal year range queries, Contains checks, and SmartDateParser for mixed real-world input.
The Bikram Sambat calendar cannot be converted to Gregorian with a formula. Months have 29 to 32 days determined by solar transits, not a fixed pattern. This post explains the lookup-table approach, the fiscal year math, and how NepDate handles it in under 5 nanoseconds.