Aled purchased a vacant rental house on January $18$ of last year. He made some improvements before showing the property to potential tenants. The work was completed on April $20$ and Aled put out a vacancy sign and began showing the property to prospective tenants that day. He received a signed lease from a new tenant on August $28,$ and the tenant moved in on September $1.$ For depreciation purposes, what is the date Aled placed this rental property in service?

January $18.$

April $20.$

August $28.$

September $1.$