Initial import

.gitignore

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+elm.js
+# Logs
+logs
+*.log
+
+# Runtime data
+pids
+*.pid
+*.seed
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directory
+# https://www.npmjs.org/doc/misc/npm-faq.html#should-i-check-my-node_modules-folder-into-git
+node_modules
+
+# Elm packages and build artifacts
+elm-stuff

elm.json

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+{
+    "type": "package",
+    "name": "rtfeldman/iso8601",
+    "summary": "Convert ISO8601 date strings to and from Posix times",
+    "license": "BSD-3-Clause",
+    "version": "1.0.0",
+    "exposed-modules": [
+        "Iso8601"
+    ],
+    "elm-version": "0.19.0 <= v < 0.20.0",
+    "dependencies": {
+        "elm-lang/core": "6.0.0 <= v < 7.0.0",
+        "elm-lang/parser": "1.0.0 <= v < 2.0.0",
+        "elm-lang/time": "1.0.0 <= v < 2.0.0"
+    },
+    "test-dependencies": {}
+}

src/Iso8601.elm

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+module Iso8601 exposing (fromTime, toTime)
+
+import Parser exposing ((|.), (|=), Parser, int, succeed, symbol)
+import Time exposing (Month(..), utc)
+
+
+{-| Convert from an ISO-8601 date string to a Posix time.
+
+ISO-8601 date strings sometimes specify things in UTC. Other times, they specify
+a non-UTC time as well as a UTC offset. I view the choice to support UTC offsets
+as a design flaw in ISO-8601 strings. This function corrects this flaw by
+normalizing dates into UTC regardless of how they were specified.
+
+For example, if an ISO-8601 date string specifies "9am in UTC+2", this function
+will return 7am UTC. The UTC offset is automatically factored in, then discarded.
+
+-}
+toTime : String -> Result Parser.Error Time.Posix
+toTime str =
+    Parser.run iso8601 str
+
+
+fromParts : Int -> Int -> Int -> Int -> Int -> Int -> Int -> Time.Posix
+fromParts year month day hour minute second ms =
+    Time.millisToPosix
+        -- TODO account for leap years
+        ((year * 365 * 24 * 60 * 60 * 1000)
+            + -- TODO calculate days-per-month accurately
+              (month * 12 * 24 * 60 * 60 * 1000)
+            + (day * 24 * 60 * 60 * 1000)
+            + (hour * 60 * 60 * 1000)
+            + (minute * 60 * 1000)
+            + (second * 1000)
+            + ms
+        )
+
+
+{-| From <https://www.timeanddate.com/date/leapyear.html>
+
+In the Gregorian calendar three criteria must be taken into account to identify leap years:
+
+  - The year can be evenly divided by 4;
+  - If the year can be evenly divided by 100, it is NOT a leap year, unless;
+  - The year is also evenly divisible by 400. Then it is a leap year.
+
+This means that in the Gregorian calendar, the years 2000 and 2400 are leap years, while 1800, 1900, 2100, 2200, 2300 and 2500 are NOT leap years.
+
+-}
+isLeapYear : Int -> Bool
+isLeapYear year =
+    (modBy 4 year == 0) && ((modBy 100 year /= 0) || (modBy 400 year == 0))
+
+
+{-| YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ
+-}
+iso8601 : Parser Time.Posix
+iso8601 =
+    -- TODO account for format variations, including those with UTC offsets
+    succeed fromParts
+        |= int
+        -- YYYY
+        |. symbol "-"
+        |= int
+        -- MM
+        |. symbol "-"
+        |= int
+        -- DD
+        |. symbol "T"
+        |= int
+        -- HH
+        |. symbol ":"
+        |= int
+        -- mm
+        |. symbol ":"
+        |= int
+        -- ss
+        |. symbol ":"
+        |= int
+        -- sss
+        |. symbol "Z"
+
+
+{-| Inflate a Posix integer into a more memory-intensive ISO-8601 date string.
+
+It's generally best to avoid doing this unless an external API requires it.
+
+(UTC integers are less error-prone, take up less memory, and are more efficient
+for time arithmetic.)
+
+Format: YYYY-MM-DDTHH:mm:ss.sssZ
+
+-}
+fromTime : Time.Posix -> String
+fromTime time =
+    ---- YYYY
+    toPaddedString 4 (Time.toYear utc time)
+        ++ "-"
+        -- MM
+        ++ fromMonth (Time.toMonth utc time)
+        ++ "-"
+        -- DD
+        ++ toPaddedString 2 (Time.toDay utc time)
+        ++ "T"
+        -- HH
+        ++ toPaddedString 2 (Time.toHour utc time)
+        ++ ":"
+        -- mm
+        ++ toPaddedString 2 (Time.toMinute utc time)
+        ++ ":"
+        -- ss
+        ++ toPaddedString 2 (Time.toSecond utc time)
+        ++ ":"
+        -- sss
+        ++ toPaddedString 2 (Time.toMillis utc time)
+        ++ "Z"
+
+
+toPaddedString digits time =
+    String.padLeft digits '0' (String.fromInt time)
+
+
+fromMonth : Time.Month -> String
+fromMonth month =
+    case month of
+        Jan ->
+            "01"
+
+        Feb ->
+            "02"
+
+        Mar ->
+            "03"
+
+        Apr ->
+            "04"
+
+        May ->
+            "05"
+
+        Jun ->
+            "06"
+
+        Jul ->
+            "07"
+
+        Aug ->
+            "08"
+
+        Sep ->
+            "09"
+
+        Oct ->
+            "10"
+
+        Nov ->
+            "11"
+
+        Dec ->
+            "12"