TASK DEFINITION: In this task, you're given passages that contain mentions of a time duration related quesry and we are supposed to write answer to a question that involves event “frequency", which refers to how often an event is likely to be repeated. For example, "taking showers" typically occurs ~5 times a week, "going to saturday market" usually happens every few weeks/months, etc. 
 Note that a lot of the questions could have more than one correct answers. We only need a single most-likely answer. Please try to keep your "answer" as simple as possible. Concise and simple "answer" is preferred over those complex and verbose ones.  
PROBLEM: Sentence: More recently, films such as Das Boot (1981), The Never Ending Story (1984) Run Lola Run (1998), Das Experiment (2001), Good Bye Lenin! (2003), Gegen die Wand (Head-on) (2004) and Der Untergang (Downfall) (2004) have enjoyed international success. In 2002 the Academy Award for Best Foreign Language Film went to Caroline Link's Nowhere in Africa, in 2007 to Florian Henckel von Donnersmarck's The Lives of Others. The Berlin International Film Festival, held yearly since 1951, is one of the world's foremost film and cinema festivals. 
Question: How often is the Berlin International Film Festival held?

SOLUTION: yearly

PROBLEM: Sentence: DST's clock shifts have the obvious disadvantage of complexity. People must remember to change their clocks; this can be time-consuming, particularly for mechanical clocks that cannot be moved backward safely. People who work across time zone boundaries need to keep track of multiple DST rules, as not all locations observe DST or observe it the same way. The length of the calendar day becomes variable; it is no longer always 24 hours. Disruption to meetings, travel, broadcasts, billing systems, and records management is common, and can be expensive. During an autumn transition from 02:00 to 01:00, a clock reads times from 01:00:00 through 01:59:59 twice, possibly leading to confusion. 
Question: During the fall time shift from 02:00 to 01:00, how many times will a clock show the times between 01:00:00 and 01:59:59?

SOLUTION: twice

PROBLEM: Sentence: Birds need to alter their metabolism in order to meet the demands of migration. The storage of energy through the accumulation of fat and the control of sleep in nocturnal migrants require special physiological adaptations. In addition, the feathers of a bird suffer from wear-and-tear and require to be molted. The timing of this molt - usually once a year but sometimes twice - varies with some species molting prior to moving to their winter grounds and others molting prior to returning to their breeding grounds. Apart from physiological adaptations, migration sometimes requires behavioural changes such as flying in flocks to reduce the energy used in migration or the risk of predation. 
Question: How often do birds molt?

SOLUTION:
usually once a year