Support 3-digit years

.travis.yml

@@ -8,5 +8,5 @@ script:
   - TZ=America/Vancouver yarn test
   - TZ=America/Los_Angeles yarn test
   - TZ=Africa/Nairobi yarn test
-  - TZ=Asia/Manila yarn test
+  - TZ=Asia/Tokyo yarn test
 sudo: false

dist/es6/helpers.d.ts

@@ -7,6 +7,7 @@ export declare const isArray: (arg: any) => arg is any[];
 export declare const range: (start: number, end?: number) => number[];
 export declare const clone: <T>(array: T[]) => T[];
 export declare const repeat: <T>(value: T | T[], times: number) => (T | T[])[];
+export declare function padStart(str: string, targetLength: number, padString?: string): string;
 /**
  * Python like split
  */

src/dateutil.ts

@@ -1,4 +1,4 @@
-import { divmod, pymod, empty, includes } from './helpers'
+import { divmod, pymod, empty, includes, padStart } from './helpers'
 
 type Datelike = Pick<Date, 'getTime'>
 
@@ -153,26 +153,22 @@ export namespace dateutil {
   }
 
   export const timeToUntilString = function (time: number) {
-    let comp
     const date = new Date(time)
-    const comps = [
-      date.getUTCFullYear(),
+    return [
+      padStart(date.getUTCFullYear().toString(), 4, '0'),
       date.getUTCMonth() + 1,
       date.getUTCDate(),
       'T',
       date.getUTCHours(),
       date.getUTCMinutes(),
       date.getUTCSeconds(),
       'Z'
-    ]
-
-    for (let i = 0; i < comps.length; i++) {
-      comp = comps[i]
-      if (!/[TZ]/.test(comp.toString()) && comp < 10) {
-        comps[i] = '0' + String(comp)
-      }
-    }
-    return comps.join('')
+    ].map(value => value.toString())
+      .map(value =>
+        /[TZ]/.test(value) ?
+          value :
+          padStart(value, 2, '0')
+      ).join('')
   }
 
   export const untilStringToDate = function (until: string) {

src/helpers.ts

@@ -41,6 +41,20 @@ export const repeat = function<T>(value: T | T[], times: number): (T | T[])[] {
   return array
 }
 
+export function padStart (str: string, targetLength: number, padString: string = ' ') {
+  targetLength = targetLength >> 0
+  if (str.length > targetLength) {
+    return String(str)
+  }
+
+  targetLength = targetLength - str.length
+  if (targetLength > padString.length) {
+    padString += repeat(padString, targetLength / padString.length)
+  }
+
+  return padString.slice(0,targetLength) + String(str)
+}
+
 /**
  * Python like split
  */

test/rrule.test.ts

@@ -3677,4 +3677,19 @@ describe('RRule', function () {
       new Date('2018-11-09T12:00:00.000Z')
     ])
   })
+
+  it('handles 3-digit years properly (#202)', () => {
+    const rrule = new RRule({
+      count: 1,
+      dtstart: new Date(Date.UTC(990, 0, 1, 0, 0, 0))
+    })
+    const ruleString = rrule.toString()
+    const rrule2 = RRule.fromString(ruleString)
+
+    expect(ruleString).to.equal('COUNT=1;DTSTART=09900101T000000Z')
+    expect(rrule2.count()).to.equal(1)
+    expect(rrule2.all()).to.deep.equal([
+      new Date(Date.UTC(990, 0, 1, 0, 0, 0))
+    ])
+  })
 })