"schedule": {
  "interval": 1,
  "interval_unit": "month",
  "max_interval": 12,
  "start_time": "2019-05-29 09:11:01 +0700"
}

JSON Attribute	Description	Type	Required
interval	Subscription's interval given by merchant.	Integer	Required
interval_unit	Interval temporal unit. Note: Supports `day`, `week`, and `month`.	String	Required
max_interval	Maximum interval of subscription. Subscription will end after maximum interval is reached. If `max_interval` is set to `0` will be executed once. If `max_interval` is `null` or omitted from the payload, the subscription will continue indefinitely until manually deactivated.	Integer	Optional
start_time	Timestamp of subscription in `yyyy-MM-dd HH:mm:ss Z`. The value must be after the current time. If specified, first payment will happen on `start_time`. If `start_time` is not specified, the default value for `start_time` will be the date after the first interval after current time.	String	Optional