cannot calculate LOS "Length of stay" after ETL run

[comorbidity]

LOS is the number of hours between period.start and period.end of a FHIR Period (usually encounter, but also other date differences). https://build.fhir.org/datatypes.html#Period

preserving HOUR level precision is therefore needed for ETL outputs.
Alternatively, LOS could be calculated within ETL but this seems difficult (as difficult) as having ETL execute case definitions.

Effort easy: use datetime instead from ETL
Effort hard: have ETL calculate LOS (much harder)

[comorbidity]

Only applies to i2b2 ETL, postponing.