code: public JsonElement serialize(Calendar src, Type typeOfSrc,
  			JsonSerializationContext context) {
  		int year = src.get(Calendar.YEAR);
  		String month = this.formatter.format(Double.valueOf(src
  				.get(Calendar.MONTH) + 1));
  		String day = this.formatter.format(Double.valueOf(src
  				.get(Calendar.DAY_OF_MONTH)));
  		String hour = this.formatter.format(Double.valueOf(src
  				.get(Calendar.HOUR_OF_DAY)));
  		String minute = this.formatter.format(Double.valueOf(src
  				.get(Calendar.MINUTE)));
  		String formattedDate = year + "-" + month + "-" + day + "T" + hour
  				+ ":" + minute;
  
  		return context.serialize(formattedDate);
  	}
docs: Serializes a Calendar using the Facebook date format (YYYY-MM-DDThh:mm).
  
  @param src
  the src
  @param typeOfSrc
  the type of src
  @param context
  the context
  @return the json element