Date and time service to help with UTC handling and formatting.

DateService.ts

import { ISecurityService } from './security';
import * as moment from 'moment-timezone';

const UTC_DATE_PARSE: string = 'YYYY-MM-DD';
export const DEFAULT_TIMEZONE: string = 'UTC';

/**
 * Provides time zone, date conversion and formatting support
 * based on the user's preferences.
 */
export interface IDateService {
  /**
   * Sets the current moment to the user's current timezone peference.
   * @param {String} [timezone] The timezone to set as the default.
   */
  setDefaultTimezone(timezone?: string): void;

  /**
   * Gets the users current timezone. Defaults to UTC if not set.
   * @returns {moment.MomentZone}
   */
  getUserTimezone(): moment.MomentZone;

  /**
   * Gets the users current timezone name. Defaults to UTC if not set.
   * @returns {String}
   */
  getUserTimezoneName(): string;

  /**
   * Attempts to guess the users timezone based on the browser.
   * @returns {moment.MomentZone}
   */
  guessTimezone(): moment.MomentZone;

  /**
   * Returns the user's current date as the UTC date.
   *
   *   We always get the start of user's current local date and then
   *   represent this as the UTC date. If we just got the current UTC
   *   date, that might not match the user's local date.
   *
   * @returns {moment.MomentZone}
   */
  getUtcDate(): moment.Moment;

  /**
   * Gets the current UTC date time.
   * @returns {moment.MomentZone}
   */
  getUtcDateTime(): moment.Moment;

  /**
   * Formats the specified moment using the user's date preference.
   * @param {moment.Moment} value The moment to format.
   * @param {String} format The format to use.
   * @returns {String}
   */
  format(value: moment.Moment, format: string): string;

  /**
   * Formats the specified moment using the user's date preference.
   * @param {moment.Moment} value The moment to format.
   * @returns {String}
   */
  formatDate(value: moment.Moment): string;

  /**
   * Formats the specified moment using the user's time preference.
   * @param {moment.Moment} value The moment to format.
   * @returns {String}
   */
  formatTime(value: moment.Moment): string;

  /**
   * Formats the specified moment using the user's date time preference.
   * @param {moment.Moment} value The moment to format.
   * @returns {String}
   */
  formatDateTime(value: moment.Moment): string;

  /**
   * Parses the specified string as a UTC moment.
   * @param {String} value The date time to parse.
   * @param {String} [format] The format of the date to parse.
   * @returns {moment.Moment}
   */
  parseUtc(value: string, format?: string): moment.Moment;

  /**
   * Parses a ISO 8601 date time string as a UTC moment.
   * @param {String} value The ISO 8601 string to parse.
   * @returns {moment.Moment}
   */
  parseIso8601(value: string): moment.Moment;
}

export class DateService implements IDateService {

  constructor(private securityService: ISecurityService) { }

  setDefaultTimezone(timezone?: string): void {
    moment.tz.setDefault(timezone || this.getUserTimezoneName());
  }

  getUserTimezone(): moment.MomentZone {
    return moment.tz.zone(this.getUserTimezoneName());
  }

  getUserTimezoneName(): string {
    return this.securityService.getCurrentUser().timezone || DEFAULT_TIMEZONE;
  }

  guessTimezone(): moment.MomentZone {
    return moment.tz.zone(moment.tz.guess() || DEFAULT_TIMEZONE);
  }

  getUtcDate(): moment.Moment {
    return moment.utc(moment().local().startOf('day').format(UTC_DATE_PARSE), UTC_DATE_PARSE);
  }

  getUtcDateTime(): moment.Moment {
    return moment.utc();
  }

  format(value: moment.Moment, format: string): string {
    return value.format(format);
  }

  formatDate(value: moment.Moment): string {

    // The date is stored as date time in UTC, there
    // is no need to convert to a local timezone as
    // its a date only component

    return value.format(this.securityService.getDateFormat());
  }

  formatTime(value: moment.Moment): string {
    return value.tz(this.getUserTimezoneName()).format(this.securityService.getTimeFormat());
  }

  formatDateTime(value: moment.Moment): string {
    return value.tz(this.getUserTimezoneName()).format(this.securityService.getDateTimeFormat());
  }

  parseUtc(value: string, format?: string): moment.Moment {
    return moment.utc(value, format);
  }

  parseIso8601(value: string): moment.Moment {
    return moment.utc(value, moment.ISO_8601);
  }
}

SecurityService.ts

import { User } from './user';

export interface ISecurityService {
  getCurrentUser(): User;
  getDateFormat(): string;
  getTimeFormat(): string;
  getDateTimeFormat(): string;
}

User.ts

export interface User {
  timezone: string;
}