ExpectedValidationError from EmbedBuilder().setTimestamp(variable)

CombinedError (3)
  Received one or more errors

  1 ExpectedValidationError > s.literal(V)
  |   Expected values to be equals
  | 
  |   Expected:
  |   | null
  | 
  |   Received:
  |   | '1695404406973'

  2 ValidationError > s.number
  |   Expected a number primitive
  | 
  |   Received:
  |   | '1695404406973'

  3 ValidationError > s.date
  |   Expected a Date
  | 
  |   Received:
  |   | '1695404406973'

export class someClass {
    public createdAt!: number
}

//...

const embed = new EmbedBuilder()
            //set a bold title
            .setTitle('**EmbedTitle**')
            .setDescription('SomeLongText')
            .setFooter({ text: 'FooterText' })
            .setTimestamp(classInstance.createdAt)

discord.js 14.13.0
@sapphire/discord.js-utilities 7.0.2
@sapphire/duration 1.1.0
@sapphire/framework 4.6.0
@sapphire/pieces 3.7.0
@sapphire/utilities 3.13.0