diff --git a/base/dates/conversions.jl b/base/dates/conversions.jl
index 22614f355f94d..22b0819b7b18c 100644
--- a/base/dates/conversions.jl
+++ b/base/dates/conversions.jl
@@ -31,30 +31,10 @@ Base.convert(::Type{DateTime}, dt::Date) = DateTime(UTM(value(dt)*86400000))
 Base.convert(::Type{Date}, dt::DateTime) = Date(UTD(days(dt)))
 Base.convert(::Type{Time}, dt::DateTime) = Time(Nanosecond((value(dt) % 86400000) * 1000000))
 
-"""
-    convert{T<:Real}(::Type{T}, dt::DateTime) -> T
-Converts a DateTime value `dt` to a number of type `T`. The returned value corresponds to the number of Rata Die milliseconds since epoch.
-See `convert(DateTime, x::Real)` for inverse.
-"""
-Base.convert{R<:Real}(::Type{R},x::DateTime) = convert(R,value(x))
-"""
-    convert{T<:Real}(::Type{T}, dt::Date) -> T
-Converts a Date value `dt` to a number of type `T`. The returned value corresponds to the number of Rata Die days since epoch.
-See `convert(Date, x::Real)` for inverse.
-"""
-Base.convert{R<:Real}(::Type{R},x::Date)     = convert(R,value(x))
-"""
-    convert{T<:Real}(::Type{DateTime}, x::T) -> DateTime
-Converts a number of type `T` to a DateTime. `x` should be the number of Rata Die milliseconds since epoch.
-See `convert(Int64,dt::DateTime)` for inverse.
-"""
-Base.convert{R<:Real}(::Type{DateTime}, x::R) = DateTime(UTM(x))
-"""
-    convert{T<:Real}(::Type{Date}, x::T) -> Date
-Converts a number of type `T` to a Date. `x` should be the number of Rata Die days since epoch.
-See `convert(Int64,dt::Date)` for inverse.
-"""
-Base.convert{R<:Real}(::Type{Date}, x::R) = Date(UTD(x))
+Base.convert(::Type{DateTime},x::Millisecond)  = DateTime(Dates.UTInstant(x))  # Converts Rata Die milliseconds to a DateTime
+Base.convert(::Type{Millisecond},dt::DateTime) = Millisecond(value(dt))        # Converts DateTime to Rata Die milliseconds
+Base.convert(::Type{Date},x::Day)  = Date(Dates.UTInstant(x))  # Converts Rata Die days to a Date
+Base.convert(::Type{Day},dt::Date) = Day(value(dt))            # Converts Date to Rata Die days
 
 ### External Conversions
 const UNIXEPOCH = value(DateTime(1970)) #Rata Die milliseconds for 1970-01-01T00:00:00
diff --git a/base/dates/periods.jl b/base/dates/periods.jl
index 935a8363cfc45..07a8c5b9fddb0 100644
--- a/base/dates/periods.jl
+++ b/base/dates/periods.jl
@@ -37,16 +37,12 @@ for period in (:Year, :Month, :Week, :Day, :Hour, :Minute, :Second, :Millisecond
         """ $period(v)
     end
 end
-# Now we're safe to define Period-Number conversions
-# Anything an Int64 can convert to, a Period can convert to
-Base.convert{T<:Number}(::Type{T},x::Period) = convert(T,value(x))
-Base.convert{T<:Period}(::Type{T},x::Real) = T(x)
 
 #Print/show/traits
 Base.string{P<:Period}(x::P) = string(value(x),_units(x))
 Base.show(io::IO,x::Period) = print(io,string(x))
 Base.zero{P<:Period}(::Union{Type{P},P}) = P(0)
-Base.one{P<:Period}(::Union{Type{P},P}) = P(1)
+Base.one{P<:Period}(::Union{Type{P},P}) = 1  # see #16116
 Base.typemin{P<:Period}(::Type{P}) = P(typemin(Int64))
 Base.typemax{P<:Period}(::Type{P}) = P(typemax(Int64))
 
@@ -54,13 +50,13 @@ Base.typemax{P<:Period}(::Type{P}) = P(typemax(Int64))
 """
     default(p::Period) -> Period
 
-Returns a sensible "default" value for the input Period by returning `one(p)` for Year,
-Month, and Day, and `zero(p)` for Hour, Minute, Second, and Millisecond.
+Returns a sensible "default" value for the input Period by returning `T(1)` for Year,
+Month, and Day, and `T(0)` for Hour, Minute, Second, and Millisecond.
 """
 function default end
 
-default{T<:DatePeriod}(p::Union{T,Type{T}}) = one(p)
-default{T<:TimePeriod}(p::Union{T,Type{T}}) = zero(p)
+default{T<:DatePeriod}(p::Union{T,Type{T}}) = T(1)
+default{T<:TimePeriod}(p::Union{T,Type{T}}) = T(0)
 
 (-){P<:Period}(x::P) = P(-value(x))
 Base.isless{P<:Period}(x::P,y::P) = isless(value(x),value(y))
diff --git a/base/dates/ranges.jl b/base/dates/ranges.jl
index 17eed2054784d..92fb4868aaad3 100644
--- a/base/dates/ranges.jl
+++ b/base/dates/ranges.jl
@@ -4,12 +4,19 @@
 
 # Override default step; otherwise it would be Millisecond(1)
 Base.colon{T<:DateTime}(start::T, stop::T) = StepRange(start, Day(1), stop)
-Base.colon{T<:Time}(start::T, stop::T) = StepRange(start, Second(1), stop)
+Base.colon{T<:Date}(start::T, stop::T)     = StepRange(start, Day(1), stop)
+Base.colon{T<:Time}(start::T, stop::T)     = StepRange(start, Second(1), stop)
+
+Base.range(start::DateTime, len::Integer)  = range(start, Day(1), len)
+Base.range(start::Date, len::Integer)      = range(start, Day(1), len)
+
+(::Type{StepRange{T,R}}){T<:Dates.DatePeriod,R<:Real}(start, step, stop) =
+    throw(ArgumentError("must specify step as a Period when constructing Dates ranges"))
 
 # Given a start and end date, how many steps/periods are in between
-guess(a::DateTime,b::DateTime,c) = floor(Int64,(Int128(b) - Int128(a)) / toms(c))
-guess(a::Date,b::Date,c) = Int64(div(Int64(b - a), days(c)))
-len(a::Time,b::Time,c) = Int64(div(Int64(b - a), tons(c)))
+guess(a::DateTime,b::DateTime,c) = floor(Int64,(Int128(value(b)) - Int128(value(a)))/toms(c))
+guess(a::Date,b::Date,c) = Int64(div(value(b - a),days(c)))
+len(a::Time,b::Time,c) = Int64(div(value(b - a), tons(c)))
 function len(a,b,c)
     lo, hi, st = min(a,b), max(a,b), abs(c)
     i = guess(a,b,c)-1
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 3f8a9f947a541..6151def6274ce 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -1773,4 +1773,17 @@ end)
 
 @deprecate EachLine(stream, ondone) EachLine(stream, ondone=ondone)
 
+# These conversions should not be defined, see #19896
+@deprecate convert{T<:Number}(::Type{T}, x::Dates.Period) convert(T, Dates.value(x))
+@deprecate convert{T<:Dates.Period}(::Type{T}, x::Real)   T(x)
+@deprecate convert{R<:Real}(::Type{R}, x::Dates.DateTime) R(Dates.value(x))
+@deprecate convert{R<:Real}(::Type{R}, x::Dates.Date)     R(Dates.value(x))
+@deprecate convert(::Type{Dates.DateTime}, x::Real)       Dates.DateTime(Dates.Millisecond(x))
+@deprecate convert(::Type{Dates.Date}, x::Real)           Dates.Date(Dates.Day(x))
+
+function colon{T<:Dates.Period}(start::T, stop::T)
+    depwarn("$start:$stop is deprecated, use $start:$T(1):$stop instead.", :colon)
+    colon(start, T(1), stop)
+end
+
 # End deprecations scheduled for 0.6
diff --git a/test/dates/conversions.jl b/test/dates/conversions.jl
index e35b8d84982c5..00c7538b5ca6b 100644
--- a/test/dates/conversions.jl
+++ b/test/dates/conversions.jl
@@ -61,11 +61,10 @@ let t = Dates.Period[Dates.Week(2), Dates.Day(14), Dates.Hour(14*24), Dates.Minu
         Pi = typeof(t[i])
         for j = 1:length(t)
             @test t[i] == t[j]
-            @test Int(convert(Pi,t[j])) == Int(t[i])
         end
         for j = i+1:length(t)
             Pj = typeof(t[j])
-            tj1 = t[j] + one(Pj)
+            tj1 = t[j] + Pj(1)
             @test t[i] < tj1
             @test_throws InexactError Pi(tj1)
             @test_throws InexactError Pj(Pi(typemax(Int64)))
@@ -74,8 +73,7 @@ let t = Dates.Period[Dates.Week(2), Dates.Day(14), Dates.Hour(14*24), Dates.Minu
     end
 end
 @test Dates.Year(3) == Dates.Month(36)
-@test Int(convert(Dates.Month, Dates.Year(3))) == 36
-@test Int(convert(Dates.Year, Dates.Month(36))) == 3
+@test_throws ErrorException Int(Dates.Month(36))  # eventually change to MethodError
 @test Dates.Year(3) < Dates.Month(37)
 @test_throws InexactError convert(Dates.Year, Dates.Month(37))
 @test_throws InexactError Dates.Month(Dates.Year(typemax(Int64)))
@@ -89,20 +87,20 @@ let dt = DateTime(1915,1,1,12)
     @test Dates.julian2datetime(julian) == dt
 end
 
-# Conversions to/from numbers
+# "Conversions" to/from numbers
 a = Dates.DateTime(2000)
 b = Dates.Date(2000)
-@test convert(Real,b) == 730120
-@test convert(Float64,b) == 730120.0
-@test convert(Int32,b) == 730120
-@test convert(Real,a) == 63082368000000
-@test convert(Float64,a) == 63082368000000.0
-@test convert(Int64,a) == 63082368000000
-@test convert(DateTime,63082368000000) == a
-@test convert(DateTime,63082368000000.0) == a
-@test convert(Date,730120) == b
-@test convert(Date,730120.0) == b
-@test convert(Date,Int32(730120)) == b
+@test Dates.value(b) == 730120
+@test Dates.value(a) == 63082368000000
+@test convert(Dates.DateTime, Dates.Millisecond(63082368000000)) == a
+@test convert(Dates.Millisecond, a) == Dates.Millisecond(63082368000000)
+@test Dates.DateTime(Dates.UTM(63082368000000)) == a
+@test Dates.DateTime(Dates.UTM(63082368000000.0)) == a
+@test convert(Dates.Date, Dates.Day(730120)) == b
+@test convert(Dates.Day, b) == Dates.Day(730120)
+@test Dates.Date(Dates.UTD(730120)) == b
+@test Dates.Date(Dates.UTD(730120.0)) == b
+@test Dates.Date(Dates.UTD(Int32(730120))) == b
 
 dt = Dates.DateTime(2000,1,1,23,59,59,50)
 t = Dates.Time(dt)
@@ -111,4 +109,4 @@ t = Dates.Time(dt)
 @test Dates.second(t) == 59
 @test Dates.millisecond(t) == 50
 @test Dates.microsecond(t) == 0
-@test Dates.nanosecond(t) == 0
\ No newline at end of file
+@test Dates.nanosecond(t) == 0
diff --git a/test/dates/periods.jl b/test/dates/periods.jl
index 55b35de23e1e9..f0e36908848b5 100644
--- a/test/dates/periods.jl
+++ b/test/dates/periods.jl
@@ -61,23 +61,6 @@ ns = Dates.Nanosecond(1)
 @test Dates.Millisecond(ms) == ms
 @test Dates.Microsecond(us) == us
 @test Dates.Nanosecond(ns) == ns
-@test typeof(Int8(y)) <: Int8
-@test typeof(UInt8(y)) <: UInt8
-@test typeof(Int16(y)) <: Int16
-@test typeof(UInt16(y)) <: UInt16
-@test typeof(Int32(y)) <: Int32
-@test typeof(UInt32(y)) <: UInt32
-@test typeof(Int64(y)) <: Int64
-@test typeof(UInt64(y)) <: UInt64
-@test typeof(Int128(y)) <: Int128
-@test typeof(UInt128(y)) <: UInt128
-@test typeof(convert(BigInt,y)) <: BigInt
-@test typeof(convert(BigFloat,y)) <: BigFloat
-@test typeof(convert(Complex,y)) <: Complex
-@test typeof(convert(Rational,y)) <: Rational
-@test typeof(Float16(y)) <: Float16
-@test typeof(Float32(y)) <: Float32
-@test typeof(Float64(y)) <: Float64
 @test Dates.Year(convert(Int8,1)) == y
 @test Dates.Year(convert(UInt8,1)) == y
 @test Dates.Year(convert(Int16,1)) == y
@@ -227,20 +210,6 @@ test = ((((((((dt + y) - m) + w) - d) + h) - mi) + s) - ms)
 @test zero(Dates.Second(10)) == Dates.Second(0)
 @test zero(Dates.Millisecond) == Dates.Millisecond(0)
 @test zero(Dates.Millisecond(10)) == Dates.Millisecond(0)
-@test one(Dates.Year) == Dates.Year(1)
-@test one(Dates.Year(10)) == Dates.Year(1)
-@test one(Dates.Month) == Dates.Month(1)
-@test one(Dates.Month(10)) == Dates.Month(1)
-@test one(Dates.Day) == Dates.Day(1)
-@test one(Dates.Day(10)) == Dates.Day(1)
-@test one(Dates.Hour) == Dates.Hour(1)
-@test one(Dates.Hour(10)) == Dates.Hour(1)
-@test one(Dates.Minute) == Dates.Minute(1)
-@test one(Dates.Minute(10)) == Dates.Minute(1)
-@test one(Dates.Second) == Dates.Second(1)
-@test one(Dates.Second(10)) == Dates.Second(1)
-@test one(Dates.Millisecond) == Dates.Millisecond(1)
-@test one(Dates.Millisecond(10)) == Dates.Millisecond(1)
 @test Dates.Year(-1) < Dates.Year(1)
 @test !(Dates.Year(-1) > Dates.Year(1))
 @test Dates.Year(1) == Dates.Year(1)
diff --git a/test/dates/ranges.jl b/test/dates/ranges.jl
index 49a0f65f95bd6..cff8d771b7de5 100644
--- a/test/dates/ranges.jl
+++ b/test/dates/ranges.jl
@@ -478,10 +478,10 @@ let n=100000
     return b
 end
 
-@test length(Dates.Year(1):Dates.Year(10)) == 10
+@test length(Dates.Year(1):Dates.Year(1):Dates.Year(10)) == 10
 @test length(Dates.Year(10):Dates.Year(-1):Dates.Year(1)) == 10
 @test length(Dates.Year(10):Dates.Year(-2):Dates.Year(1)) == 5
-@test_throws OverflowError length(typemin(Dates.Year):typemax(Dates.Year))
+@test_throws OverflowError length(typemin(Dates.Year):Dates.Year(1):typemax(Dates.Year))
 @test_throws MethodError Dates.Date(0):Dates.DateTime(2000)
 @test_throws MethodError Dates.Date(0):Dates.Year(10)
 @test length(range(Dates.Date(2000),366)) == 366