Some questions about the time expression task

[weikang-wang]

Sorry ,I am not a native English speaker. So, what's the difference between type“Calendar-Interval” and type “Period”.

Meantime, FBI agents and Metropolitan Police officers assigned to a joint terrorism task force here scanned the crowd of anti-abortion protesters at the annual March for Life on Capitol Hill, because Kopp has been either a participant in or arrested at this march in each of the last three years, according to another law enforcement official,

last three years

years is "Calendar-Interval" type

An ambitious expansion has left Magna with excess capacity and a heavy debt load as the automotive industry enters a downturn. The company has reported declines in operating profit in each of the past three years, despite steady sales growth.

years is "Calendar-Interval" type

Mr. Obama said later at a news conference in Amman that he had spoken to both leaders over the past two years about how it was in the interests of both countries to restore normal relations.

years is "Period" type

And there are more cases in both types, such as months .
I am very confused.

[bethard]

The difference between Calendar-Interval and Period is whether the interval is aligned to a calendar year (i.e., starting in January and ending in December) or is the same length as a year, but not necessarily aligned to the calendar year. This is a hard call and is one of thing things that is challenging for both annotators and systems.

That said, I think the presence of "each of the" in your first two cases, at least to my ear, suggests that they're talking about calendar years, while in the last case, where that is not present, I read it as the two-year interval that ends on the day of the news conference (so, not aligned to a calendar year).

[weikang-wang]

Thank you，and I have another question.

seasonal trends, seasonal market, Seasonal rains

Is the word "seasonal" in Calendar-Interval type ？

[bethard]

No, the word "seasonal" is a Season-Of-Year.

[weikang-wang]

per hour, per day, per month, per year

So these are Calendar-Interval type, isn't it ?

[bethard]

Yes, that's correct. In "per month", the "month" would be annotated as a Calendar-Interval. Similarly for the others.

[weikang-wang]

Thanks，and last question

recent three-year average
the coming year

Are two "year " “Calendar-Interval” or type “Period” ?

[bethard]

The second is usually a Calendar-Interval. The first is a harder call without more context. If the averages are averages over the entire year, then that should probably also be a Calendar-Interval.