src/vs/platform/storage/electron-main/storageMain.ts/GlobalStorageMain/updateTelemetryState
class GlobalStorageMain:	private updateTelemetryState(storage: IStorage): void {

		// First session date (once)
		const firstSessionDate = storage.get(firstSessionDateStorageKey, undefined);
		if (firstSessionDate === undefined) {
			storage.set(firstSessionDateStorageKey, new Date().toUTCString());
		}

		// Last / current session (always)
		// previous session date was the "current" one at that time
		// current session date is "now"
		const lastSessionDate = storage.get(currentSessionDateStorageKey, undefined);
		const currentSessionDate = new Date().toUTCString();
		storage.set(lastSessionDateStorageKey, typeof lastSessionDate === 'undefined' ? null : lastSessionDate);
		storage.set(currentSessionDateStorageKey, currentSessionDate);
	}