feat: adds tzDate fn, tz format option

Author: justin-schroeder

src/__tests__/addDay.spec.ts

@@ -0,0 +1,12 @@
+import { describe, it, expect } from "vitest"
+import { addDay } from "../addDay"
+process.env.TZ = "America/New_York"
+
+describe("addDay", () => {
+  it("gets the next day at the beginning of the month", () => {
+    expect(addDay("2022-01-01").toISOString()).toBe("2022-01-02T05:00:00.000Z")
+  })
+  it("gets the next day at the end of the year", () => {
+    expect(addDay("2022-12-31").toISOString()).toBe("2023-01-01T05:00:00.000Z")
+  })
+})

src/__tests__/addHour.spec.ts

@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest"
+import { addHour } from "../addHour"
+process.env.TZ = "America/New_York"
+
+describe("addHour", () => {
+  it("can increment a normal hour", () => {
+    expect(addHour("2022-01-01T00:00:00Z").toISOString()).toBe(
+      "2022-01-01T01:00:00.000Z"
+    )
+  })
+  it("can increment the last hours of the day into a new day", () => {
+    expect(addHour("2022-01-01T23:11:00Z", 3).toISOString()).toBe(
+      "2022-01-02T02:11:00.000Z"
+    )
+  })
+})

src/__tests__/addMinute.spec.ts

@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest"
+import { addMinute } from "../addMinute"
+process.env.TZ = "America/New_York"
+
+describe("addMinute", () => {
+  it("can increment a normal hour", () => {
+    expect(addMinute("2022-01-01T00:00:00Z").toISOString()).toBe(
+      "2022-01-01T00:01:00.000Z"
+    )
+  })
+  it("can increment the last hours of the day into a new day", () => {
+    expect(addMinute("2022-01-01T23:11:00Z", 181).toISOString()).toBe(
+      "2022-01-02T02:12:00.000Z"
+    )
+  })
+})

src/__tests__/addMonth.spec.ts

@@ -0,0 +1,38 @@
+import { describe, it, expect } from "vitest"
+import { addMonth } from "../addMonth"
+process.env.TZ = "America/New_York"
+
+describe("addMonth", () => {
+  it("gets the next month on the first", () => {
+    expect(addMonth("2022-01-01").toISOString()).toBe(
+      "2022-02-01T05:00:00.000Z"
+    )
+  })
+  it("can overflow a month month when the next month has fewer days", () => {
+    expect(addMonth("2000-01-31", 1, true).toISOString()).toBe(
+      "2000-03-02T05:00:00.000Z"
+    )
+  })
+  it("goe to the same day of the month on the next month", () => {
+    expect(addMonth("2000-06-04").toISOString()).toBe(
+      "2000-07-04T04:00:00.000Z"
+    )
+  })
+
+  it("can add multiple months by passing a second argument", () => {
+    expect(addMonth("2000-01-01", 2).toISOString()).toBe(
+      "2000-03-01T05:00:00.000Z"
+    )
+  })
+
+  it("can add years months by passing a second argument", () => {
+    expect(addMonth("2000-01-01", 25).toISOString()).toBe(
+      "2002-02-01T05:00:00.000Z"
+    )
+  })
+  it("can prevent month overflow with third argument", () => {
+    expect(addMonth("2020-01-31", 1, false).toISOString()).toBe(
+      "2020-02-29T05:00:00.000Z"
+    )
+  })
+})

src/__tests__/addSecond.spec.ts

@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest"
+import { addSecond } from "../addSecond"
+process.env.TZ = "America/New_York"
+
+describe("addSecond", () => {
+  it("can increment a normal hour", () => {
+    expect(addSecond("2022-01-01T00:00:00Z").toISOString()).toBe(
+      "2022-01-01T00:00:01.000Z"
+    )
+  })
+  it("can increment the last hours of the day into a new day", () => {
+    expect(addSecond("2022-01-01T23:11:00Z", 3600 * 3 + 1).toISOString()).toBe(
+      "2022-01-02T02:11:01.000Z"
+    )
+  })
+})

src/__tests__/addYear.spec.ts

@@ -0,0 +1,19 @@
+import { describe, it, expect } from "vitest"
+import { addYear } from "../addYear"
+process.env.TZ = "America/New_York"
+
+describe("addYear", () => {
+  it("can add a year to a Date object by default", () => {
+    const d = new Date("2000-12-17T12:00:00")
+    const h: number = d.getTimezoneOffset() / 60
+    expect(addYear(d).toISOString()).toBe(`2001-12-17T${12 + h}:00:00.000Z`)
+  })
+  it("can subtract a year to a Date", () => {
+    const d = new Date("2000-12-17T12:00:00")
+    const h: number = d.getTimezoneOffset() / 60
+    expect(addYear(d, -1).toISOString()).toBe(`1999-12-17T${12 + h}:00:00.000Z`)
+  })
+  it("can overflow the day of the month on leap year", () => {
+    expect(addYear("2000-02-29").toISOString()).toBe("2001-02-28T05:00:00.000Z")
+  })
+})

src/__tests__/applyOffset.spec.ts

@@ -0,0 +1,17 @@
+import { describe, it, expect } from "vitest"
+import { applyOffset } from "../applyOffset"
+process.env.TZ = "America/New_York"
+
+describe("applyOffset", () => {
+  it("can apply a negative offset to a date", () => {
+    expect(applyOffset("2023-02-22T00:00:00Z", "-0500").toISOString()).toBe(
+      "2023-02-21T19:00:00.000Z"
+    )
+  })
+
+  it("can apply a positive offset to a date", () => {
+    expect(applyOffset("2023-04-13T10:15:00", "+0200").toISOString()).toBe(
+      "2023-04-13T16:15:00.000Z"
+    )
+  })
+})

src/__tests__/date.spec.ts

@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest"
+import { date } from "../date"
+
+process.env.TZ = "America/New_York"
+describe("date", () => {
+  it("qualifies and re-timezones a date", () => {
+    expect(date("2022-01-22 00:00:00").toISOString()).toBe(
+      "2022-01-22T05:00:00.000Z"
+    )
+  })
+  it("accepts a time with a timezone offset", () => {
+    expect(date("2022-01-22T00:00-0300").toISOString()).toBe(
+      "2022-01-22T03:00:00.000Z"
+    )
+  })
+})

src/__tests__/dayEnd.spec.ts

@@ -0,0 +1,11 @@
+import { describe, it, expect } from "vitest"
+import { dayEnd } from "../dayEnd"
+process.env.TZ = "America/New_York"
+
+describe("dayEnd", () => {
+  it("can become the start of the day", () => {
+    expect(dayEnd("2023-02-22T12:00:00Z").toISOString()).toBe(
+      "2023-02-23T04:59:59.999Z"
+    )
+  })
+})

src/__tests__/dayOfYear.spec.ts

@@ -0,0 +1,12 @@
+import { describe, it, expect } from "vitest"
+import { dayOfYear } from "../dayOfYear"
+process.env.TZ = "America/New_York"
+
+describe("dayOfYear", () => {
+  it("can find the number of days in a year", () => {
+    expect(dayOfYear("2023-08-01")).toBe(213)
+  })
+  it("can find the number of days in a year", () => {
+    expect(dayOfYear("2020-08-01")).toBe(214)
+  })
+})