the start or beginning of …
the onset of …
the end of …
at any time
at any given time
at any one time
the first stage of …
concurrent
simultaneous
a contemporary account of …
Shakespeare’s etc. contemporary
consecutive
in chronological order
the project was completed on time
Duration
between … and …
from … to …
an interval of … seconds, hours etc.
over the course of … five weeks, one year etc.
a 24-hour period
for or during the entire period
during the study
for the duration of the experiment
to change over time
to evolve over time
a brief period of …
a rapid development
a time of rapid change
a swift decision to …
a continuous process of …
chronic poverty, illness etc.
a temporary measure
… is only a short-term solution to …
… has been plagued by short-termism
a long-term problem
long-term change proved to be more difficult …
a or one persistent problem in … is …
… eventually led to …
in the long run
a permanent solution
The problem was eventually solved by …
a period of stability or great change
the … period is usually defined as …
the Elizabethan etc. era is or was characterized US and GB or characterised GB by …
… spans several decades or centuries
an age of …
a new epoch
the end of an epoch