Refactoring: Split shared types into seperate modules and document alot.

server/shared/utils/time.ts

@@ -0,0 +1,28 @@
+/**
+ * Utility functions for "wibbly wobbly timey wimey" stuff.
+ */
+import { UnixTimestampMilliseconds, UnixTimestampSeconds } from "../types";
+
+/**
+ * Converts an {@link UnixTimestampMilliseconds} to an {@link UnixTimestampSeconds} rounding down.
+ *
+ * @param ms - The timestamp in milliseconds.
+ * @returns - The timestamp in seconds.
+ */
+export function toUnixTimestampSeconds(
+    ms: UnixTimestampMilliseconds
+): UnixTimestampSeconds {
+    return Math.floor(ms / 1000) as UnixTimestampSeconds;
+}
+
+/**
+ * Converts an {@link UnixTimestampSeconds} to an {@link UnixTimestampMilliseconds}.
+ *
+ * @param s - The timestamp in seconds.
+ * @returns - The timestamp in milliseconds.
+ */
+export function toUnixTimestampMilliseconds(
+    s: UnixTimestampSeconds
+): UnixTimestampMilliseconds {
+    return (s * 1000) as UnixTimestampMilliseconds;
+}