Temporal Mechanization

Our mission is to prove the correctness of a selection of the functions in the ECMAScript Temporal Proposal. Note: Based on our findings, the specification text of the proposal will be updated in the nearest future. Our mechanization is based on a previous version of the specification (the most recent snapshot of which was available on October 16th, 2025).

Developers

• Aria Bjørnbakken Eide
• Vebjørn Søreide Øiestad

Supervisor

• Mikhail Barash

Creating Makefile and Building Project

$ rocq makefile -f _CoqProject -o Makefile
$ make

or just

$ ./build.sh

Mechanized Functions

Section 3

• 3.5.1 ISO Date Records
• 3.5.2 CreateISODateRecord
• 3.5.6 RegulateISODate
• 3.5.7 IsValidISODate
• 3.5.9 PadISOYear
• 3.5.10 TemporalDateToString
• 3.5.12 CompareISODate

Section 4

• 4.5.1 Time Records
• 4.5.2 CreateTimeRecord
• 4.5.3 MidnightTimeRecord
• 4.5.4 NoonTimeRecord
• 4.5.9 IsValidTime
• 4.5.10 BalanceTime
• 4.5.13 TimeRecordToString
• 4.5.14 CompareTimeRecord
• 4.5.15 AddTime

Section 5

• 5.5.1 ISO Date-Time Records
• 5.5.3 CombineISODateAndTimeRecord
• 5.5.9 ISODateTimeToString
• 5.5.10 CompareISODateTime

Section 7

• 7.5.1 Date Duration Records
• 7.5.14 DateDurationSign
• 7.5.21 TimeDurationFromComponents
• 7.5.22 AddTimeDuration
• 7.5.23 Add24HourDaysToTimeDuration
• 7.5.24 AddTimeDurationToEpochNanoseconds
• 7.5.25 CompareTimeDuration
• 7.5.26 TimeDurationFromEpochNanosecondsDifference
• 7.5.28 TimeDurationSign

Section 8

• 8.5.1 IsValidEpochNanoseconds
• 8.5.4 CompareEpochNanoseconds

Section 9

• 9.5.1 ISO Year-Month Records
• 9.5.3 ISOYearMonthWithinLimits
• 9.5.4 BalanceISOYearMonth

Section 11

• 11.1.5 FormatOffsetTimeZoneIdentifier
• 11.1.6 FormatUTCOffsetNanoseconds

Section 12

• 12.1 Calendar Types
• 12.3.15 FormatCalendarAnnotation
• 12.3.17 ISODaysInMonth

Section 13

• 13.2 EpochDaysToEpochMs
• 13.3 Date Equations
• 13.8 NegateRoundingMode
• 13.14 ValidateTemporalRoundingIncrement
• 13.20 LargerOfTwoTemporalUnits
• 13.21 IsCalendarUnit
• 13.22 TemporalUnitCategory
• 13.23 MaximumTemporalDurationRoundingIncrement
• 13.25 FormatFractionalSeconds
• 13.26 FormatTimeString
• 13.27 GetUnsignedRoundingMode

Inconsistencies

• 3.5.1 ISODateRecord_IsValidISODate_not_guaranteed
• 4.5.10 BalanceTime_creates_invalid_TimeRecord
• 11.1.5 FormatOffsetTimeZoneIdentifier_hour_outside_bounds_of_FormatTimeString
• 11.1.6 FormatUTCOffsetNanoseconds_hour_outside_bounds_of_FormatTimeString

Other Findings

• 7.5.21 TimeDurationFromComponents_nanoseconds'_outside_bounds_of_MaxTimeDuration
• 7.5.26 TimeDurationFromEpochNanosecondsDifference_result_outside_bounds_of_MaxTimeDuration

Notes

• 5.5.3 CombineISODateAndTimeRecord

Theorems

Proven

• RegulateISODate_never_throws_on_constrain
• PadISOYear_result_length_at_least_4
• BalanceTime_IsValidTime
• DateDurationSign_year_sign_dominates
• CompareISODate_eq_zero
• CompareISODate_eq_implies_eq_zero
• CompareTimeRecord_eq_zero
• AddTime_adding_zero_no_change

Unproven

• TemporalDateToString_without_calendar_satisfies_rfc3339
• ISODateTimeToString_without_calendar_satisfies_rfc3339
• CompareTimeRecord_eq_implies_eq_zero