What it means
というもの follows a time expression to emphasize the whole span of time, often conveying “for the entire period of” or “throughout the past.” It commonly appears with expressions such as この数日, ここ数年, or 三週間, and is especially useful when describing a continuing state, repeated event, or notable change during that period. It is more emphatic and literary than a plain duration expression with に or は.
Usage note
Do not confuse this use with というものだ, which can mean “it is that...” or express a definition or conclusion. In this pattern, the phrase before というもの must normally be a time period or an expression understood as one.
How to use it
この二週間というもの、研究室に泊まり込んでいます。
For these past two weeks, I have been staying overnight at the laboratory.
この二週間というもの、研究室に泊まり込んでいる。
For these past two weeks, I have been staying overnight at the laboratory.
Example sentences
この三日というもの、強い雨が降り続いて、川の水位が上がった。
For these past three days, heavy rain continued to fall, and the river's water level rose.
ここ数年というもの、地域の図書館では電子書籍の利用者が増えている。
For the past several years, the number of users of electronic books at local libraries has been increasing.