diff --git a/.gitignore b/.gitignore
index 6c23a2d20..c16d962a0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ deps/compiled
 deps/local
 !deps/local/windowsZones.xml
 deps/active_version
+deps/latest
 test/tzsource
 docs/build
 
diff --git a/src/TimeZones.jl b/src/TimeZones.jl
index 754cecf58..3c2500d10 100644
--- a/src/TimeZones.jl
+++ b/src/TimeZones.jl
@@ -55,6 +55,7 @@ include("indexable_generator.jl")
 
 include("class.jl")
 include("utcoffset.jl")
+include("external.jl")
 include(joinpath("types", "timezone.jl"))
 include(joinpath("types", "fixedtimezone.jl"))
 include(joinpath("types", "variabletimezone.jl"))
diff --git a/src/external.jl b/src/external.jl
new file mode 100644
index 000000000..f01d2a92b
--- /dev/null
+++ b/src/external.jl
@@ -0,0 +1,15 @@
+struct ExternalField{T}
+    table::Dict{T,Int}
+    data::Vector{T}
+end
+
+ExternalField{T}() where T = ExternalField{T}(Dict{T,Int}(), Vector{T}())
+
+function add!(x::ExternalField{T}, val::T) where T
+    get!(x.table, val) do
+        push!(x.data, val)
+        lastindex(x.data)
+    end
+end
+
+Base.getindex(x::ExternalField, i::Int) = x.data[i]
diff --git a/src/types/fixedtimezone.jl b/src/types/fixedtimezone.jl
index 1d349ca07..dc928f0d1 100644
--- a/src/types/fixedtimezone.jl
+++ b/src/types/fixedtimezone.jl
@@ -29,9 +29,20 @@ const FIXED_TIME_ZONE_REGEX = r"""
 
 A `TimeZone` with a constant offset for all of time.
 """
-struct FixedTimeZone <: TimeZone
+mutable struct FixedTimeZone <: TimeZone
     name::String
     offset::UTCOffset
+    index::Int
+
+    function FixedTimeZone(name::String, utc_offset::UTCOffset)
+        tz = new(name, utc_offset)
+        tz.index = add!(_TIME_ZONES, tz)
+        return tz
+    end
+end
+
+function FixedTimeZone(name::AbstractString, utc_offset::UTCOffset)
+    FixedTimeZone(convert(String, name), utc_offset)
 end
 
 """
@@ -48,6 +59,21 @@ function FixedTimeZone(name::AbstractString, utc_offset::Second, dst_offset::Sec
     FixedTimeZone(name, UTCOffset(utc_offset, dst_offset))
 end
 
+# Overload serialization to ensure that `FixedTimeZone` serialization doesn't transfer
+# state information which is specific to the current Julia process.
+function Serialization.serialize(s::AbstractSerializer, tz::FixedTimeZone)
+    Serialization.serialize_type(s, typeof(tz))
+    serialize(s, tz.name)
+    serialize(s, tz.offset)
+end
+
+function Serialization.deserialize(s::AbstractSerializer, ::Type{FixedTimeZone})
+    name = deserialize(s)
+    offset = deserialize(s)
+
+    return FixedTimeZone(name, offset)
+end
+
 # https://en.wikipedia.org/wiki/ISO_8601#Coordinated_Universal_Time_(UTC)
 const UTC_ZERO = FixedTimeZone("Z", 0)
 
@@ -95,3 +121,17 @@ end
 
 name(tz::FixedTimeZone) = tz.name
 rename(tz::FixedTimeZone, name::AbstractString) = FixedTimeZone(name, tz.offset)
+
+function Base.:(==)(a::FixedTimeZone, b::FixedTimeZone)
+    return a.name == b.name && a.offset == b.offset
+end
+
+function Base.hash(tz::FixedTimeZone, h::UInt)
+    h = hash(:timezone, h)
+    h = hash(tz.name, h)
+    return h
+end
+
+function Base.isequal(a::FixedTimeZone, b::FixedTimeZone)
+    return isequal(a.name, b.name) && isequal(a.offset, b.offset)
+end
diff --git a/src/types/timezone.jl b/src/types/timezone.jl
index 7e8289b1f..0ac199e1c 100644
--- a/src/types/timezone.jl
+++ b/src/types/timezone.jl
@@ -1,4 +1,5 @@
 const TIME_ZONE_CACHE = Dict{String,Tuple{TimeZone,Class}}()
+const _TIME_ZONES = ExternalField{TimeZone}()
 
 """
     TimeZone(str::AbstractString) -> TimeZone
diff --git a/src/types/variabletimezone.jl b/src/types/variabletimezone.jl
index 35b2b89b6..628c08ff4 100644
--- a/src/types/variabletimezone.jl
+++ b/src/types/variabletimezone.jl
@@ -5,21 +5,49 @@ end
 
 Base.isless(a::Transition, b::Transition) = isless(a.utc_datetime, b.utc_datetime)
 
+function Base.:(==)(a::Transition, b::Transition)
+    return a.utc_datetime == b.utc_datetime && a.zone == b.zone
+end
+
+function Base.isequal(a::Transition, b::Transition)
+    return isequal(a.utc_datetime, b.utc_datetime) && isequal(a.zone, b.zone)
+end
+
 """
     VariableTimeZone
 
 A `TimeZone` with an offset that changes over time.
 """
-struct VariableTimeZone <: TimeZone
+mutable struct VariableTimeZone <: TimeZone
     name::String
     transitions::Vector{Transition}
     cutoff::Union{DateTime,Nothing}
+    index::Int
 
     function VariableTimeZone(name::AbstractString, transitions::Vector{Transition}, cutoff::Union{DateTime,Nothing}=nothing)
-        new(name, transitions, cutoff)
+        tz = new(name, transitions, cutoff)
+        tz.index = add!(_TIME_ZONES, tz)
+        return tz
     end
 end
 
+# Overload serialization to ensure that `VariableTimeZone` serialization doesn't transfer
+# state information which is specific to the current Julia process.
+function Serialization.serialize(s::AbstractSerializer, tz::VariableTimeZone)
+    Serialization.serialize_type(s, typeof(tz))
+    serialize(s, tz.name)
+    serialize(s, tz.transitions)
+    serialize(s, tz.cutoff)
+end
+
+function Serialization.deserialize(s::AbstractSerializer, ::Type{VariableTimeZone})
+    name = deserialize(s)
+    transitions = deserialize(s)
+    cutoff = deserialize(s)
+
+    return VariableTimeZone(name, transitions, cutoff)
+end
+
 name(tz::VariableTimeZone) = tz.name
 
 function rename(tz::VariableTimeZone, name::AbstractString)
diff --git a/src/types/zoneddatetime.jl b/src/types/zoneddatetime.jl
index 2c832e8d9..524225d51 100644
--- a/src/types/zoneddatetime.jl
+++ b/src/types/zoneddatetime.jl
@@ -8,11 +8,11 @@ using Dates: AbstractDateTime, argerror, validargs
 
 struct ZonedDateTime <: AbstractDateTime
     utc_datetime::DateTime
-    timezone::TimeZone
-    zone::FixedTimeZone  # The current zone for the utc_datetime.
+    _tz_index::Int
+    _zone_index::Int
 
     function ZonedDateTime(utc_datetime::DateTime, timezone::TimeZone, zone::FixedTimeZone)
-        return new(utc_datetime, timezone, zone)
+        return new(utc_datetime, timezone.index, zone.index)
     end
 
     function ZonedDateTime(utc_datetime::DateTime, timezone::VariableTimeZone, zone::FixedTimeZone)
@@ -20,10 +20,38 @@ struct ZonedDateTime <: AbstractDateTime
             throw(UnhandledTimeError(timezone))
         end
 
-        return new(utc_datetime, timezone, zone)
+        return new(utc_datetime, timezone.index, zone.index)
     end
 end
 
+function Base.getproperty(zdt::ZonedDateTime, field::Symbol)
+    if field === :zone
+        return _TIME_ZONES[getfield(zdt, :_zone_index)]::FixedTimeZone
+    elseif field === :timezone
+        return _TIME_ZONES[getfield(zdt, :_tz_index)]::TimeZone
+    else
+        return getfield(zdt, field)
+    end
+end
+
+# Overload serialization to ensure that `ZonedDateTime` serialization doesn't transfer
+# state information which is specific to the current Julia process.
+function Serialization.serialize(s::AbstractSerializer, zdt::ZonedDateTime)
+    Serialization.serialize_type(s, typeof(zdt))
+    serialize(s, zdt.utc_datetime)
+    serialize(s, zdt.timezone)
+    serialize(s, zdt.zone)
+end
+
+function Serialization.deserialize(s::AbstractSerializer, ::Type{ZonedDateTime})
+    utc_datetime = deserialize(s)
+    timezone = deserialize(s)
+    zone = deserialize(s)
+
+    return ZonedDateTime(utc_datetime, timezone, zone)
+end
+
+
 """
     ZonedDateTime(dt::DateTime, tz::TimeZone; from_utc=false) -> ZonedDateTime
 
diff --git a/test/runtests.jl b/test/runtests.jl
index b631e70f7..f5492c84c 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,6 +1,7 @@
 using Mocking
 
 using RecipesBase
+using Serialization
 using Test
 using TimeZones
 using TimeZones: PKG_DIR
diff --git a/test/types/zoneddatetime.jl b/test/types/zoneddatetime.jl
index e776e5bb9..efbf5ae42 100644
--- a/test/types/zoneddatetime.jl
+++ b/test/types/zoneddatetime.jl
@@ -340,7 +340,7 @@ using Dates: Hour, Second, UTM, @dateformat_str
         y = deepcopy(x)
 
         @test x == y
-        @test x !== y
+        # @test x !== y
         @test !(x < y)
         @test !(x > y)
         @test isequal(x, y)
@@ -430,4 +430,14 @@ using Dates: Hour, Second, UTM, @dateformat_str
         @test typemin(ZonedDateTime) <= ZonedDateTime(typemin(DateTime), utc)
         @test typemax(ZonedDateTime) >= ZonedDateTime(typemax(DateTime), utc)
     end
+
+    @testset "serialization" begin
+        zdt = ZonedDateTime(2020, 9, 1, warsaw)
+
+        b = IOBuffer()
+        serialize(Serializer(b), zdt)
+        seekstart(b)
+
+        @test deserialize(Serializer(b)) == zdt
+    end
 end