Re: [calsify] JSCalendar: fractional seconds

["Robert Stepanek" <[e-mail]>]

This is a draft specification, happy about any input:

2.1. FRACSEC parameter

 Parameter name: FRACSEC

 Purpose: This parameter is used to define fractional seconds for
 time values and durations. It is meant to preserve time precision
 on time values and duration with sub-second precision, without
 increasing the time value range within iCalendar.

 Description: This parameter MAY be specified on properties of type
 DATE-TIME or DURATION. The integral part of the float value MUST
 be zero. The value MUST NOT be negative. iCalendar
 implementations MAY ignore this parameter in date time arithmetic.
 Implementations MUST ignore presence of the FRACSEC parameter on
 RECURRENCE-ID properties when determining recurrence overrides.
 If present on a RECURRENCE-ID property, its value MUST match the
 FRACSEC parameter value on the DTSTART property.

 Format Definition:

 This parameter is defined by the following notation:

 fracsec-param = float

 Example: DTSTART;FRACSEC=0.03:20190605T133015



On Thu, Jun 6, 2019, at 1:56 PM, Ken Murchison wrote:
> As a related topic, a libical user/developer submitted a PR to add millisecond precision to time values. I haven’t committed it because it simply changes the DATETIME values which certainly isn’t backwards compatible. I suggested a new VALUE type but even that isn’t compatible with unaware clients. 
> 
> Regardless, there does appear to be *some* desire to have fractional seconds support in iCalendar. 
> 
> --
> Kenneth Murchison
> Cyrus Development Team
> FastMail US LLC
> [e-mail]
> 
> 
> 
> On Thu, Jun 6, 2019, at 8:04 AM, Marten Gajda wrote:
>> Is this parameter is meant to preserve the fractional seconds for round-trips or are iCalendar clients encouraged to use the value?

>> I mean, would a client that's aware of X-FRACSEC have to match RECURRENCE-IDs ,RDATES and EXDATES taking the fractional seconds into account? 

>> I think we should advise against that and make clear that this is not meant to increase the precision of times in iCalendar, but merely to preserve it.

>> Btw, how do we cope with unaware clients doing partial updates? I.e. a client which is not aware of X-FRACSEC adds a new recurrence-override (not adding X-FRACSEC to RECURRENCE-ID). When being converted back to JSCalendar, this would result in an additional instance instead of an override.

>> Marten

>> Am 06.06.19 um 13:49 schrieb Robert Stepanek:
>>> It just occurred to me that the current JSCalendar RFC draft ambiguously defines if fractional seconds are allowed in the LocalDate time type.
>>> 
>>> To be clear: we intend to allow fractional seconds in the start property (and any other LocalDate property). The next version of the RFC draft will define this more clearly.
>>> 
>>> Unfortunately, fractional second date-times and durations can not be round-tripped out of the box with iCalendar. We will define an iCalendar extension parameter in the informational guide for mapping iCalendar and JSCalendar (draft-ietf-calext-jscalendar-icalendar):
>>>  * X-FRACSEC of value type INTEGER
>>>  * This parameter MAY be set on iCalendar properties of type DATE-TIME or DURATION. It MUST NOT be set more than once per property.
>>>  * The value of this parameter defines the fractional seconds of the DATE-TIME or DURATION type.
>>>  * This will allow iCalendar implementations not being aware of this extension parameter to display the time value "good enough" with second precision.
>>> 
>>> Please let me know if you prefer another approach.
>>> 
>>> Cheers,
>>> Robert
>>> 
>>> _______________________________________________
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>>> https://www.ietf.org/mailman/listinfo/calsify
>>> 
>> -- 
Marten Gajda
CEO

dmfs GmbH
Schandauer Straße 34
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GERMANY

phone: [phone]
email: [e-mail]

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