reader.go

package main

import (
	"encoding/csv"
	"fmt"
	"io"
	"log"
	"os"
	"strconv"
	"time"
)

type timeFixer struct {
	prev       time.Time
	adjustment time.Duration
}

func (t *timeFixer) parseBrokenTime(s string) (ts time.Time, err error) {
	localTs, err := strconv.ParseInt(s, 10, 64)
	if err != nil {
		return
	}
	// Fix time
	realTs := time.Unix(localTs, 0).Add(-2 * time.Hour).UTC()

	diff := realTs.Sub(t.prev)
	t.prev = realTs
	switch diff {
	case 0 * time.Hour:
		// DST backward; following data in standard time
		fmt.Printf("WARN: Detected DST backward shift %v\n", realTs)
		t.adjustment = 0 * time.Hour
		//realTs = realTs.Add(-1 * time.Hour)
	case 1 * time.Hour:
		// Normal case
	case 2 * time.Hour:
		// DST forward, following data in summer time
		t.adjustment = 1 * time.Hour
		fmt.Printf("WARN: Detected DST forward shift %v\n", realTs)
	default:
		fmt.Printf("WARN: Records missing, now %v %v\n", realTs, diff)
		_, offset := realTs.Local().Zone()
		t.adjustment = time.Duration(offset/3600-2) * time.Hour
		fmt.Printf("WARN: Offset now %v\n", t.adjustment)
	}

	realTs = realTs.Add(-t.adjustment)

	return realTs, nil
}

func main() {
	file, err := os.Open("power.csv") // For read access.
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()
	r := csv.NewReader(file)

	var fixer timeFixer
	for {
		record, err := r.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatal(err)
		}
		if len(record) != 2 {
			log.Fatal("Invalid file format, expected two columns")
		}
		ts, err := fixer.parseBrokenTime(record[0])
		if err != nil {
			log.Fatal(err)
		}
		fmt.Println(ts, record[1])
	}
}

Z_README.txt

[joneskoo@grant energiatili]$ go run reader.go power.csv |grep WARN                  
WARN: Records missing, now 2011-12-31 22:00:00 +0000 UTC 2562047h47m16.854775807s
WARN: Offset now 0
WARN: Detected DST forward shift 2012-03-25 02:00:00 +0000 UTC
WARN: Records missing, now 2014-09-02 22:00:00 +0000 UTC 18265h0m0s
WARN: Offset now 1h0m0s
WARN: Detected DST backward shift 2014-10-26 01:00:00 +0000 UTC
WARN: Detected DST forward shift 2015-03-29 02:00:00 +0000 UTC
WARN: Detected DST backward shift 2015-10-25 01:00:00 +0000 UTC
WARN: Detected DST forward shift 2016-03-27 02:00:00 +0000 UTC
[joneskoo@grant energiatili]$ go run reader.go power.csv |grep -v '0$'|tail -n 20
2016-06-27 02:00:00 +0000 UTC 1.097
2016-06-27 03:00:00 +0000 UTC 0.261
2016-06-27 04:00:00 +0000 UTC 1.145
2016-06-27 05:00:00 +0000 UTC 1.045
2016-06-27 06:00:00 +0000 UTC 0.879
2016-06-27 07:00:00 +0000 UTC 1.438
2016-06-27 08:00:00 +0000 UTC 1.352
2016-06-27 09:00:00 +0000 UTC 1.6
2016-06-27 10:00:00 +0000 UTC 0.885
2016-06-27 11:00:00 +0000 UTC 0.267
2016-06-27 12:00:00 +0000 UTC 0.85
2016-06-27 13:00:00 +0000 UTC 0.528
2016-06-27 14:00:00 +0000 UTC 0.395
2016-06-27 15:00:00 +0000 UTC 1.806
2016-06-27 16:00:00 +0000 UTC 1.036
2016-06-27 17:00:00 +0000 UTC 1.42
2016-06-27 18:00:00 +0000 UTC 1.015
2016-06-27 19:00:00 +0000 UTC 0.355
2016-06-27 20:00:00 +0000 UTC 1.021
2016-06-27 21:00:00 +0000 UTC 0.358