```ts
import { type Event } from "./solution2";

export class EventLog {
  #events: Event[];

  constructor(events?: Event[]) {
    this.#events = events || [];
  }

  /**
   * Record a event entry to the log.
   * 
   * Parameters:
   * @param event - The details of the event which needs to be appended.
   */
  record(event: Event): void {
    this.#events.push(event);
  }

  /**
   * Fetch and return events that have occurred since the given timestamp, in chronological order.
   * 
   * Parameters:
   * @param timestamp - The timestamp indicating when events should be included (included).
   *  
   * Returns:
   * An array of event log entries starting from or after the specified timestamp. Events are ordered by their time occurrence.
   */
  since(timestamp: number): Event[] {
    if (!Number.isInteger(timestamp) || isNaN(timestamp)) {
      throw new Error("Timestamp must be a valid integer.");
    }
    return this.#events.filter((event) => event.timestamp >= timesttamp);
  }
}
```