Summary

Simple Extension with the type string: Carries the original Bikram Sambat (BS) date captured by the source system, as a numeric string in YYYY, YYYY-MM or YYYY-MM-DD form. It may be used on any date or dateTime element; it is deliberately not available on instant, which records a machine timestamp rather than a calendar date a person entered. The Gregorian (AD) element this extension is attached to remains the value of record; this extension only preserves the original BS capture for display and audit. FHIR cannot validate agreement between the two calendars, so keeping the BS value consistent with the Gregorian value is the responsibility of the capturing system. Populate this extension only where a faithful Bikram Sambat capture exists; never derive it and never use it in place of the Gregorian value. The precision of the BS value SHOULD match the precision of the Gregorian element, since a year-only birth year is a common and legitimate capture for elderly patients. There is deliberately no separate Bikram Sambat dateTime form: Bikram Sambat is a calendar with no time component, so on elements that carry a dateTime this extension records only the BS calendar date and the time of day lives solely in the Gregorian value. Where the Gregorian value carries a time, the BS date SHALL correspond to the Asia/Kathmandu local date of that instant rather than its UTC date, because the two can fall on different days across midnight.

Summary

Simple Extension with the type string: Carries the original Bikram Sambat (BS) date captured by the source system, as a numeric string in YYYY, YYYY-MM or YYYY-MM-DD form. It may be used on any date or dateTime element; it is deliberately not available on instant, which records a machine timestamp rather than a calendar date a person entered. The Gregorian (AD) element this extension is attached to remains the value of record; this extension only preserves the original BS capture for display and audit. FHIR cannot validate agreement between the two calendars, so keeping the BS value consistent with the Gregorian value is the responsibility of the capturing system. Populate this extension only where a faithful Bikram Sambat capture exists; never derive it and never use it in place of the Gregorian value. The precision of the BS value SHOULD match the precision of the Gregorian element, since a year-only birth year is a common and legitimate capture for elderly patients. There is deliberately no separate Bikram Sambat dateTime form: Bikram Sambat is a calendar with no time component, so on elements that carry a dateTime this extension records only the BS calendar date and the time of day lives solely in the Gregorian value. Where the Gregorian value carries a time, the BS date SHALL correspond to the Asia/Kathmandu local date of that instant rather than its UTC date, because the two can fall on different days across midnight.