What does it mean by 'interim deadline'?
We didn't foresee that worrying about that would mean that the construction work fell behind and the contractors didn't meet one of their interim deadlines.

Question

Answer

The contractors have a job to do, and this job has been broken into smaller tasks which each have their own deadlines. It's a way to organise their time more efficiently and not focus on the main deadline at the end of the whole job.

In Chinese the nearest term might be '临时期限‘.

Answer

-before reaching the appointed time, in the meantime 
-provisional date, before the main one