diff --git a/Project.toml b/Project.toml
index d23b55e..ce5a89f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "UnixTimes"
 uuid = "ab1a18e7-b408-4913-896c-624bb82ed7f4"
 authors = ["Christian Rorvik <christian.rorvik@gmail.com>"]
-version = "1.4.1"
+version = "1.5.0"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
diff --git a/src/UnixTimes.jl b/src/UnixTimes.jl
index 198d330..d5468d2 100644
--- a/src/UnixTimes.jl
+++ b/src/UnixTimes.jl
@@ -63,11 +63,24 @@ UnixTime(x::Date) = UnixTime(DateTime(x))
 UnixTime(x::Date, y::Time) =
     UnixTime(year(x), month(x), day(x), hour(y), minute(y), second(y), millisecond(y), microsecond(y), nanosecond(y))
 
+const DATEFORMAT = dateformat"yyyy-mm-ddTHH:MM:SS.sss"
+
+function UnixTime(s::AbstractString)
+    try
+        @assert length(s) == 29
+        dt = DateTime(chop(s; tail=6), DATEFORMAT)
+        ns = Nanosecond(parse(Int, last(s, 6)))
+        UnixTime(dt) + ns
+    catch
+        throw(ArgumentError("Invalid UnixTime string"))
+    end
+end
+
 Base.convert(::Type{UnixTime}, x::DateTime) = UnixTime(x)
 
 function Base.show(io::IO, x::UnixTime)
     xdt = convert(DateTime, x)
-    print(io, Dates.format(xdt, dateformat"yyyy-mm-ddTHH:MM:SS.sss"))
+    print(io, Dates.format(xdt, DATEFORMAT))
     v = x.instant.periods.value
     d = 100_000
     for i in 1:6
diff --git a/test/runtests.jl b/test/runtests.jl
index 19b5d3e..ef499a8 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -47,6 +47,10 @@ end
 @testset "io" begin
     x = UnixTime(2020, 1, 2, 3, 4, 5, 6, 7, 8)
     @test string(x) == "2020-01-02T03:04:05.006007008"
+    @test UnixTime(string(x)) == x
+    @test_throws ArgumentError UnixTime("2025-01-28T15:49:36.5901397023")
+    @test_throws ArgumentError UnixTime("2025-01-28T15:49:36.59013970")
+    @test_throws ArgumentError UnixTime(repeat("a", 29))
 end
 
 @testset "arithmetic" begin