The following tables list the Transact-SQL date and time functions. See Deterministic and Nondeterministic Functions for more information about determinism. Transact-SQL derives all system date and time values from the operating system of the computer on which the instance of SQL Server runs.
SQL Server The accuracy depends on the computer hardware and version of Windows on which the instance of SQL Server running. This API has a precision fixed at nanoseconds. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services.
Privacy policy. Skip to main content. And isinstance method will give you True in all cases. If you need to distinguish datetime from date you should check name of the class. I've faced with this problem when i have different formatting rules for dates and dates with time. If your existing code is already relying on from datetime import datetime , you can also simply also import date.
In Python 3. This is due to the fact that datetime is a subclass of date and as it is explained in this other answer:. Therefore, when distinguishing between datetime and date , type should be used instead:. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Python: how can I check whether an object is of type datetime.
Ask Question. Asked 8 years, 6 months ago. Active 3 months ago. Viewed k times. I have tried a few obvious options but none of them works: In []: x Out[]: datetime. Improve this question. I should think a four- or five-line program would suffice. The system clock on Windows 7 and Windows 8 systems has a resolution of approximately 15 milliseconds. This resolution affects small time intervals less than milliseconds. The following example illustrates the dependence of current date and time values on the resolution of the system clock.
In the example, an outer loop repeats 20 times, and an inner loop serves to delay the outer loop. If the value of the outer loop counter is 10, a call to the Thread. Sleep method introduces a five-millisecond delay. The following example shows the number of milliseconds returned by the DateTime. Milliseconds property changes only after the call to Thread.
A calculation using a DateTime structure, such as Add or Subtract , does not modify the value of the structure. Instead, the calculation returns a new DateTime structure whose value is the result of the calculation. Conversion operations between time zones such as between UTC and local time, or between one time zone and another take daylight saving time into account, but arithmetic and comparison operations do not. The DateTime structure itself offers limited support for converting from one time zone to another.
However, a full set of time zone conversion methods is available in the TimeZoneInfo class. You convert the time in any one of the world's time zones to the time in any other time zone using these methods. Calculations and comparisons of DateTime objects are meaningful only if the objects represent times in the same time zone. You can use a TimeZoneInfo object to represent a DateTime value's time zone, although the two are loosely coupled. A DateTime object does not have a property that returns an object that represents that date and time value's time zone.
In a time zone-aware application, you must rely on some external mechanism to determine the time zone in which a DateTime object was created. You could use a structure that wraps both the DateTime value and the TimeZoneInfo object that represents the DateTime value's time zone.
Each DateTime member implicitly uses the Gregorian calendar to perform its operation. Exceptions are methods that implicitly specify a calendar. These include constructors that specify a calendar, and methods with a parameter derived from IFormatProvider , such as System. Operations by members of the DateTime type take into account details such as leap years and the number of days in a month. They are:. Each culture uses a default calendar defined by its read-only CultureInfo.
Calendar property. Each culture may support one or more calendars defined by its read-only CultureInfo. OptionalCalendars property. It must be one of the calendars found in the CultureInfo. OptionalCalendars array. A culture's current calendar is used in all formatting operations for that culture. For example, the default calendar of the Thai Buddhist culture is the Thai Buddhist Era calendar, which is represented by the ThaiBuddhistCalendar class.
When a CultureInfo object that represents the Thai Buddhist culture is used in a date and time formatting operation, the Thai Buddhist Era calendar is used by default. Calendar property is changed, as the following example shows:. A culture's current calendar is also used in all parsing operations for that culture, as the following example shows.
You instantiate a DateTime value using the date and time elements number of the year, month, and day of a specific calendar by calling a DateTime constructor that includes a calendar parameter and passing it a Calendar object that represents that calendar. The following example uses the date and time elements from the ThaiBuddhistCalendar calendar. DateTime constructors that do not include a calendar parameter assume that the date and time elements are expressed as units in the Gregorian calendar.
All other DateTime properties and methods use the Gregorian calendar. For example, the DateTime. Year property returns the year in the Gregorian calendar, and the DateTime. IsLeapYear Int32 method assumes that the year parameter is a year in the Gregorian calendar. Each DateTime member that uses the Gregorian calendar has a corresponding member of the Calendar class that uses a specific calendar. For example, the Calendar.
GetYear method returns the year in a specific calendar, and the Calendar. IsLeapYear method interprets the year parameter as a year number in a specific calendar. The following example uses both the DateTime and the corresponding members of the ThaiBuddhistCalendar class. It does not include a member that allows you to retrieve the week number of the year. To retrieve the week of the year, call the individual calendar's Calendar.
GetWeekOfYear method. The following example provides an illustration. For more information on dates and calendars, see Working with Calendars. You can persist DateTime values in four ways:. You must ensure that the routine that restores the DateTime values doesn't lose data or throw an exception regardless of which technique you choose.
DateTime values should round-trip. That is, the original value and the restored value should be the same. And if the original DateTime value represents a single instant of time, it should identify the same moment of time when it's restored. To successfully restore DateTime values that are persisted as strings, follow these rules:.
Make the same assumptions about culture-specific formatting when you restore the string as when you persisted it. To ensure that a string can be restored on a system whose current culture is different from the culture of the system it was saved on, call the ToString overload to save the string by using the conventions of the invariant culture. If the date represents a single moment of time, ensure that it represents the same moment in time when it's restored, even on a different time zone.
You can also serialize the value along with time zone information. For more information about this approach, see Serializing DateTime and time zone data. The most common error made when persisting DateTime values as strings is to rely on the formatting conventions of the default or current culture. Problems arise if the current culture is different when saving and restoring the strings. The following example illustrates these problems. It saves five dates using the formatting conventions of the current culture, which in this case is English United States.
It restores the dates using the formatting conventions of a different culture, which in this case is English Great Britain. Because the formatting conventions of the two cultures are different, two of the dates can't be restored, and the remaining three dates are interpreted incorrectly. Also, if the original date and time values represent single moments in time, the restored times are incorrect because time zone information is lost.
To round-trip DateTime values successfully, follow these steps:. To restore the persisted DateTime values without data loss, follow these steps:. The following example uses the invariant culture and the "O" standard format string to ensure that DateTime values saved and restored represent the same moment in time regardless of the system, culture, or time zone of the source and target systems.
You can persist a date and time as an Int64 value that represents a number of ticks. In this case, you don't have to consider the culture of the systems the DateTime values are persisted and restored on. To persist a DateTime value as an integer:.
To restore a DateTime value that has been persisted as an integer:. The following example persists an array of DateTime values as integers on a system in the U. Pacific Time zone. It restores it on a system in the UTC zone. The file that contains the integers includes an Int32 value that indicates the total number of Int64 values that immediately follow it. You can persist DateTime values through serialization to a stream or file, and then restore them through deserialization.
DateTime data is serialized in some specified object format. The objects are restored when they are deserialized. A formatter or serializer, such as XmlSerializer or BinaryFormatter , handles the process of serialization and deserialization. For more information about serialization and the types of serialization supported by the.
NET Framework, see Serialization. The following example uses the XmlSerializer class to serialize and deserialize DateTime values. The values represent all leap year days in the twenty-first century.
The output represents the result if the example is run on a system whose current culture is English Great Britain. Because you've deserialized the DateTime object itself, the code doesn't have to handle cultural differences in date and time formats. The previous example doesn't include time information. If a DateTime value represents a moment in time and is expressed as a local time, convert it from local time to UTC before serializing it by calling the ToUniversalTime method.
The following example uses the BinaryFormatter class to serialize DateTime data on a system in the U. Pacific Standard Time zone and to deserialize it on a system in the U. Central Standard zone. The time zone can be set on a per-connection basis. As long as the time zone setting remains constant, you get back the same value you store. This occurs because the same time zone was not used for conversion in both directions. For more information, see Section 5.
In MySQL 8. See Section 9. For complete information regarding syntax and additional examples, see the description of the CAST function. In some cases, this syntax can be deceiving. For example, a value such as '' might look like a time value because of the : , but is interpreted as the year '' if used in date context. The value '' is converted to '' because '45' is not a valid month. The only delimiter recognized between a date and time part and a fractional seconds part is the decimal point.
The server requires that month and day values be valid, and not merely in the range 1 to 12 and 1 to 31, respectively.
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