Recently there have been a lot of researches for summarizing news stream and
for detecting edges of new events in the news stream.
But, in these tasks, all data are assumed to carry timestamp
(temporal information). It is noteworthy that
news articles without timestamp can't make any contribution to these tasks.
In this investigation, we propose a new technique to estimate timestamps
to any news articles using small number of incomplete news corpus.
Here we learn temporal information and topic information by means of both
EM algorithm and incremental clustering,
then we estimate timestamp of news article based on events
that are discussed in news corpus. In this work,
we examine TDT2 corpus and we show how well
our approach works by some experiments.