In the exercise/workout where you translate the phrases from English to German:
"One needs a bike in Berlin. You(i) have to buy one tomorrow".
My answer was: "Man braucht in Berlin ein Fahrrad. Du musst EINS MORGEN kaufen" because I was following the structure provided in a past lesson: "subject + verb + DIRECT OBJECT PRONOUN + indirect obj (noun/pronoun) + TIME + manner + place + direct object noun + infinitive/past participle".
However, my answer was not accepted. The correct answer was: "Man braucht in Berlin ein Fahrrad. Du musst MORGEN EINS kaufen", which does not follow the structure. If I understood correctly, "eins" is a direct object pronoun. Am I missing something? What is the reason why "morgen" (time) comes before "eins"?

Thanks.