The past can only be known, not changed. The future can only be changed, not known.
Ken, who is a graduate student, went to the United States last year.
Also many incidents of robbery by threats and violence are occurring.
Saturday is the pottery class I've been attending since last year.
In the blink of an eye, the tennis-ball-sized dumpling had disappeared.
The Labor Party's vote increased at last year's election.
With the subjunctive past all the 'be' verbs become 'were', OK?
The example is a past progressive tense sentence. How was everybody taught when they were learning about progressive tense?
They contacted the station staff but the man had left the area and gone out through the ticket barrier.
The present perfect expresses the long span from past to present.
I would like to draw your attention to the fact that Kanjisho uses multiple sources of data provided by third parties.
The search results are provided by the wonderful Jisho API which itself uses various data sources which you can find on the jisho's website. The data concerning the kanji strokes are provided by the KanjiVG project, under the CC BY 3.0 FR license. I also use Tatoeba to provide example sentences and Kuroshiro to obtain the furiganas and romajis versions of the sentences.
If you find any vices, errors or malfunctions, please let me know so that I can correct them.