ObsPy Tutorial

Handling Time

Authors:¶

Lion Krischer (@krischer)
Tobias Megies (@megies)

This is a bit dry but not very difficult and important to know. It is used everywhere in ObsPy!

All absolute time values are consistently handled with this class
Based on a double precision POSIX timestamp for accuracy
Timezone can be specified at initialization (if necessary)
In Coordinated Universal Time (UTC) so no need to deal with timezones, daylight savings, ...

%matplotlib inline
import matplotlib.pyplot as plt
plt.style.use('ggplot')
plt.rcParams['figure.figsize'] = 12, 8

Features of `UTCDateTime`¶

Initialization¶

from obspy import UTCDateTime

print(UTCDateTime("2011-03-11T05:46:23.2"))        # mostly time strings defined by ISO standard
print(UTCDateTime("2011-03-11T14:46:23.2+09:00"))  # non-UTC timezone input
print(UTCDateTime(2011, 3, 11, 5, 46, 23, 2))
print(UTCDateTime(1299822383.2))

# Current time can be initialized by leaving out any arguments
print(UTCDateTime())

Attribute Access¶

time = UTCDateTime("2011-03-11T05:46:23.200000Z")
print(time.year)
print(time.julday)
print(time.timestamp)
print(time.weekday)
# try time.<Tab>

Handling time differences¶

"+/-" defined to add seconds to an UTCDateTime object
"-" defined to get time difference of two UTCDateTime objects

time = UTCDateTime("2011-03-11T05:46:23.200000Z")
print(time)

# one hour later
print(time + 3600)

time2 = UTCDateTime(2012, 1, 1)
print(time2 - time)

Exercises¶

Calculate the number of days passed since the Tohoku main shock (the timestamp used above).

Make a list of 10 UTCDateTime objects, starting today at 10:00 with a spacing of 90 minutes.

Below is a list of strings with origin times of magnitude 8+ earthquakes since 2000 (fetched from IRIS). Assemble a list of interevent times in days. Use matplotlib to display a histogram.