The static typing rules for fn:sum at the end of section 7.2.10 of formal semantics contains the following judgment:

statEnv |-  Type2 <: xs:anyAtomicType ?
Type3 = prime(Type1)
Type4 = convert_untypedAtomic(Type3, xs:double)
FormalItemType 1, ...,FormalItemType n = Type4
statEnv |-  FormalItemType 1 can be promoted to Type0
...
statEnv |-  FormalItemType n can be promoted to Type0
statEnv |-  Type2 <: Type0
Type0 in { xs:integer, xs:decimal, xs:float, xs:double, xs:yearMonthDuration }
------------------------------------------------------------------------------
statEnv |-  (FN-URI,"sum")(Type1,Type2) : Type0 · aggregate_quantifier(quantifier(Type1))

The line

Type0 in { xs:integer, xs:decimal, xs:float, xs:double, xs:yearMonthDuration }

should read

Type0 in { xs:integer, xs:decimal, xs:float, xs:double, xs:yearMonthDuration, xs:dayTimeDuration }

to keep in line with the text.