Input: Frédéric Chopin
At the end of November, Chopin returned to Paris. He passed the winter in unremitting illness, but gave occasional lessons and was visited by friends, including Delacroix and Franchomme. Occasionally he played, or accompanied the singing of Delfina Potocka, for his friends. During the summer of 1849, his friends found him an apartment in Chaillot, out of the centre of the city, for which the rent was secretly subsidised by an admirer, Princess Obreskoff. Here in June 1849 he was visited by Jenny Lind.

When did Jenny Lind visit Chopin?
Output: June 1849

Input: Ashkenazi Jews
Speculation that the Ashkenazi arose from Khazar stock surfaced in the later 19th century and has met with mixed fortunes in the scholarly literature. In late 2012 Eran Elhaik, a research associate studying genetics at the Johns Hopkins University School of Public Health, argued for Khazar descent in his paper The Missing Link of Jewish European Ancestry: Contrasting the Rhineland and the Khazarian Hypotheses. A 2013 study of Ashkenazi mitochondrial DNA found no significant evidence of Khazar contribution to the Ashkenazi Jewish DNA, as would be predicted by the Khazar hypothesis.

When did the idea that the Ashkenazi may have come from Khazar stock come about?
Output: in the later 19th century

Input: Royal assent
During the 1960s, the ceremony of assenting by commission was discontinued and is now only employed once a year, at the end of the annual parliamentary session. In 1960, the Gentleman Usher of the Black Rod arrived to summon the House of Commons during a heated debate and several members protested against the disruption by refusing to attend the ceremony. The debacle was repeated in 1965; this time, when the Speaker left the chair to go to the House of Lords, some members continued to make speeches. As a result, the Royal Assent Act 1967 was passed, creating an additional form for the granting of royal assent. As the attorney-general explained, "there has been a good deal of resentment not only at the loss of Parliamentary time that has been involved but at the breaking of the thread of a possibly eloquent speech and the disruption of a debate that may be caused." The granting of assent by the monarch in person, or by commission, is still possible, but this third form is used on a day-to-day basis.

What was passed in reference to the discord in 1960 and 1965 during assention cremonies?
Output: Royal Assent Act 1967

Input: Circadian rhythm
Studies by Nathaniel Kleitman in 1938 and by Derk-Jan Dijk and Charles Czeisler in the 1990s put human subjects on enforced 28-hour sleep–wake cycles, in constant dim light and with other time cues suppressed, for over a month. Because normal people cannot entrain to a 28-hour day in dim light if at all,[citation needed] this is referred to as a forced desynchrony protocol. Sleep and wake episodes are uncoupled from the endogenous circadian period of about 24.18 hours and researchers are allowed to assess the effects of circadian phase on aspects of sleep and wakefulness including sleep latency and other functions.[page needed]

How long did the suppression of time clues study last?
Output:
month