feat(datetime): add month and day of week constants

Author: a-skua

datetime/constants.ts

@@ -56,3 +56,212 @@ export const DAY: number = HOUR * 24;
  * ```
  */
 export const WEEK: number = DAY * 7;
+/**
+ * The month index for January.
+ *
+ * @example
+ * ```ts
+ * import { JAN } from "@std/datetime/constants";
+ *
+ * JAN; // 0
+ * ```
+ */
+export const JAN = 0;
+/**
+ * The month index for February.
+ *
+ * @example
+ * ```ts
+ * import { FEB } from "@std/datetime/constants";
+ *
+ * FEB; // 1
+ * ```
+ */
+export const FEB = 1;
+/**
+ * The month index for March.
+ *
+ * @example
+ * ```ts
+ * import { MAR } from "@std/datetime/constants";
+ *
+ * MAR; // 2
+ * ```
+ */
+export const MAR = 2;
+/**
+ * The month index for April.
+ *
+ * @example
+ * ```ts
+ * import { APR } from "@std/datetime/constants";
+ *
+ * APR; // 3
+ * ```
+ */
+export const APR = 3;
+/**
+ * The month index for May.
+ *
+ * @example
+ * ```ts
+ * import { MAY } from "@std/datetime/constants";
+ *
+ * MAY; // 4
+ * ```
+ */
+export const MAY = 4;
+/**
+ * The month index for June.
+ *
+ * @example
+ * ```ts
+ * import { JUN } from "@std/datetime/constants";
+ *
+ * JUN; // 5
+ * ```
+ */
+export const JUN = 5;
+/**
+ * The month index for July.
+ *
+ * @example
+ * ```ts
+ * import { JUL } from "@std/datetime/constants";
+ *
+ * JUL; // 6
+ * ```
+ */
+export const JUL = 6;
+/**
+ * The month index for August.
+ *
+ * @example
+ * ```ts
+ * import { AUG } from "@std/datetime/constants";
+ *
+ * AUG; // 7
+ * ```
+ */
+export const AUG = 7;
+/**
+ * The month index for September.
+ *
+ * @example
+ * ```ts
+ * import { SEP } from "@std/datetime/constants";
+ *
+ * SEP; // 8
+ * ```
+ */
+export const SEP = 8;
+/**
+ * The month index for October.
+ *
+ * @example
+ * ```ts
+ * import { OCT } from "@std/datetime/constants";
+ *
+ * OCT; // 9
+ * ```
+ */
+export const OCT = 9;
+/**
+ * The month index for November.
+ *
+ * @example
+ * ```ts
+ * import { NOV } from "@std/datetime/constants";
+ *
+ * NOV; // 10
+ * ```
+ */
+export const NOV = 10;
+/**
+ * The month index for December.
+ *
+ * @example
+ * ```ts
+ * import { DEC } from "@std/datetime/constants";
+ *
+ * DEC; // 11
+ * ```
+ */
+export const DEC = 11;
+/**
+ * The day of week index for Sunday.
+ *
+ * @example
+ * ```ts
+ * import { SUN } from "@std/datetime/constants";
+ *
+ * SUN; // 0
+ * ```
+ */
+export const SUN = 0;
+/**
+ * The day of week index for Monday.
+ *
+ * @example
+ * ```ts
+ * import { MON } from "@std/datetime/constants";
+ *
+ * MON; // 1
+ * ```
+ */
+export const MON = 1;
+/**
+ * The day of week index for Tuesday.
+ *
+ * @example
+ * ```ts
+ * import { TUE } from "@std/datetime/constants";
+ *
+ * TUE; // 2
+ * ```
+ */
+export const TUE = 2;
+/**
+ * The day of week index for Wednesday.
+ *
+ * @example
+ * ```ts
+ * import { WED } from "@std/datetime/constants";
+ *
+ * WED; // 3
+ * ```
+ */
+export const WED = 3;
+/**
+ * The day of week index for Thursday.
+ *
+ * @example
+ * ```ts
+ * import { THU } from "@std/datetime/constants";
+ *
+ * THU; // 4
+ * ```
+ */
+export const THU = 4;
+/**
+ * The day of week index for Friday.
+ *
+ * @example
+ * ```ts
+ * import { FRI } from "@std/datetime/constants";
+ *
+ * FRI; // 5
+ * ```
+ */
+export const FRI = 5;
+/**
+ * The day of week index for Saturday.
+ *
+ * @example
+ * ```ts
+ * import { SAT } from "@std/datetime/constants";
+ *
+ * SAT; // 6
+ * ```
+ */
+export const SAT = 6;