diff --git a/src/period.jl b/src/period.jl
index 539f66e..deccdef 100644
--- a/src/period.jl
+++ b/src/period.jl
@@ -52,6 +52,12 @@ end
     return sum(divi[1:length(tuf)] .* tuf)
 end
 
+"""
+    days,h,mi,s,ms,... = timetuplefrac(t::Period)
+
+Return a tuple with the number of whole days, hours (`h`), minutes (`mi`),
+seconds (`s`) and millisecods (`ms`),... from the time period `t`.
+"""
 function timetuplefrac(t::Period{T,Tfactor}) where {T,Tfactor}
     # for integers
     factor = _factor(t)
diff --git a/src/query.jl b/src/query.jl
index 2cc1919..68fa3fd 100644
--- a/src/query.jl
+++ b/src/query.jl
@@ -1,23 +1,5 @@
 # query functions
 
-@inline isleap(::Type{DateTimeAllLeap},year,has_year_zero) = true
-@inline isleap(::Type{DateTimeNoLeap},year,has_year_zero) = false
-
-@inline function isleap(::Type{DateTimeProlepticGregorian},year,has_year_zero)
-    if (year < 0) && !has_year_zero
-        year = year + 1
-    end
-    return (year % 400 == 0) || ((year % 4 == 0) && (year % 100 !== 0))
-end
-
-@inline function isleap(::Type{DateTimeJulian},year,has_year_zero)
-    if (year < 0) && !has_year_zero
-        year = year + 1
-    end
-    return year % 4 == 0
-end
-
-
 # https://web.archive.org/web/20240304171516/https://unidata.github.io/cftime/api.html
 # https://github.com/cf-convention/cf-conventions/issues/298
 @inline _hasyear0(::Type{T}) where T <: Union{DateTimeJulian,DateTimeStandard} = false
diff --git a/test/reference_algorithm.jl b/test/reference_algorithm.jl
index 55e8cd8..5b06f1e 100644
--- a/test/reference_algorithm.jl
+++ b/test/reference_algorithm.jl
@@ -1,15 +1,40 @@
 module Reference
 
+import CFTime
 import CFTime:
     DateTimeJulian,
     DateTimeProlepticGregorian,
-    _hasyear0,
-    isleap
+    DateTimeStandard,
+    DateTimeNoLeap,
+    DateTimeAllLeap,
+    DateTime360Day,
+    _hasyear0
 
-# Adapted
-# from https://github.com/Unidata/cftime/blob/dc75368cd02bbcd1352dbecfef10404a58683f94/src/cftime/_cftime.pyx
-# Licence MIT
-# by Jeff Whitaker (https://github.com/jswhit)
+@inline isleap(::Type{DateTimeAllLeap},year,has_year_zero) = true
+@inline isleap(::Type{DateTimeNoLeap},year,has_year_zero) = false
+@inline isleap(::Type{DateTime360Day},year,has_year_zero) = false
+
+@inline function isleap(::Type{DateTimeProlepticGregorian},year,has_year_zero)
+    if (year < 0) && !has_year_zero
+        year = year + 1
+    end
+    return (year % 400 == 0) || ((year % 4 == 0) && (year % 100 !== 0))
+end
+
+@inline function isleap(::Type{DateTimeJulian},year,has_year_zero)
+    if (year < 0) && !has_year_zero
+        year = year + 1
+    end
+    return year % 4 == 0
+end
+
+@inline function isleap(::Type{DateTimeStandard},year,has_year_zero)
+    if year < 1582
+        isleap(DateTimeJulian,year,has_year_zero)
+    else
+        isleap(DateTimeProlepticGregorian,year,has_year_zero)
+    end
+end
 
 @inline function month_lengths(::Type{T}, year::Integer, has_year_zero) where T
     if isleap(T, year, has_year_zero)
@@ -19,11 +44,19 @@ import CFTime:
     end
 end
 
+function month_lengths(::Type{DateTime360Day}, year::Integer, has_year_zero)
+    ntuple(i -> 30,12)
+end
+
+# Adapted
+# from https://github.com/Unidata/cftime/blob/dc75368cd02bbcd1352dbecfef10404a58683f94/src/cftime/_cftime.pyx
+# Licence MIT
+# by Jeff Whitaker (https://github.com/jswhit)
+
 
 @inline function datetuple_ymd(::Type{T}, delta_days, julian_gregorian_mixed, has_year_zero) where T
-    year = 1858
-    month = 11
-    day = 17
+    # use the same origin
+    year,month,day = CFTime.datetuple_ymd(T,0)
 
     month_length = month_lengths(T, year, has_year_zero)
 
@@ -34,8 +67,14 @@ end
             0
         end
 
+    # The Julian calendar day Thursday, 4 October 1582 was
+    # followed by the first day of the Gregorian calendar,
+    # Friday, 15 October 1582
+
+    # counting down
     @inbounds while delta_days < 0
         if (year == 1582) && (month == 10) && (day > 14) && (day + delta_days < 15)
+            #@show n_invalid_dates
             delta_days -= n_invalid_dates    # skip over invalid dates
         end
 
@@ -61,6 +100,7 @@ end
 
     @inbounds while delta_days > 0
         if (year == 1582) && (month == 10) && (day < 5) && (day + delta_days > 4)
+            #@show n_invalid_dates
             delta_days += n_invalid_dates    # skip over invalid dates
         end
 
@@ -86,10 +126,10 @@ end
     return year,month,day
 end
 
-function datetuple_ymd(::Type{DateTimeProlepticGregorian},Z)
-    has_year_zero = _hasyear0(DateTimeProlepticGregorian)
-    julian_gregorian_mixed = false
-    return datetuple_ymd(DateTimeProlepticGregorian, Z, julian_gregorian_mixed, has_year_zero)
+function datetuple_ymd(::Type{T},Z) where T
+    has_year_zero = _hasyear0(T)
+    julian_gregorian_mixed = T <: DateTimeStandard
+    return datetuple_ymd(T, Z, julian_gregorian_mixed, has_year_zero)
 end
 
 end
diff --git a/test/test_time.jl b/test/test_time.jl
index 1123e86..ed39435 100644
--- a/test/test_time.jl
+++ b/test/test_time.jl
@@ -484,15 +484,17 @@ for T in [DateTimeStandard, DateTimeJulian, DateTimeProlepticGregorian,
 end
 
 
+# comparision with reference algorithm
+#Δ = 1
+Δ = 1000
 
-Z = CFTime.datenum(DateTimeProlepticGregorian,-1000,1,1):CFTime.datenum(DateTimeProlepticGregorian,4000,1,1)
-
-Z = CFTime.datenum(DateTimeProlepticGregorian,-1000,1,1):100:CFTime.datenum(DateTimeProlepticGregorian,4000,1,1)
-
-MYMD = CFTime.datetuple_ymd.(DateTimeProlepticGregorian,Z);
-RYMD = Reference.datetuple_ymd.(DateTimeProlepticGregorian,Z);
-
-@test MYMD == RYMD
+for T in [DateTimeStandard, DateTimeJulian, DateTimeProlepticGregorian,
+          DateTimeAllLeap, DateTimeNoLeap, DateTime360Day]
+    Z = CFTime.datenum(T,-1000,1,1):Δ:CFTime.datenum(T,4000,1,1)
+    MYMD = CFTime.datetuple_ymd.(T,Z);
+    RYMD = Reference.datetuple_ymd.(T,Z);
+    @test MYMD == RYMD
+end
 
 #=
 for dt = DateTime(-1000,1,1):Day(100):DateTime(2300,3,1)