Making a timer, 32.768kHz+555+DT_INT. Good idea?

[ScaleRobotics]

.... or if there is any other cheaper way to overcome this problem, I don't want to go for expensive RTC ICs.

How about cheap RTC ICs? The MCP79410 RTCs are under $1.00 in singles. I got a few samples but have not tried them yet. http://www.microchip.com/en_US/techn...ock/index.html Downside is soic is as big as it gets, no dips. Cheapest from Microchip Direct: http://www.microchipdirect.com/Produ...words=mcp79410

Features:
• Real-Time Clock/Calendar (RTCC), Battery
Backed:
- Hours, Minutes, Seconds, Day of Week, Day,
Month and Year
- Dual alarm with single output
• On-Chip Digital Trimming/Calibration:
- Range -127 to +127 ppm
- Resolution 1 ppm
• Programmable Open-Drain Output Control:
- CLKOUT with 4 selectable frequencies
- Alarm output
• 64 Bytes SRAM, Battery Backed
• 1 Kbits EEPROM (128x8):
- 8 bytes/page
- Block/sector write protection
- Protect none, 1/4, 1/2 or all of array
• Separate 64-Bit Unique ID:
- User or factory programmable
- Protected area
- EUI-48™ or EUI-64™ MAC address
- Custom ID programming
• Automatic VCC Switchover to VBAT Backup
Supply
• Power-Fail Time-Stamp for Battery Switchover
• Low-Power CMOS Technology:
- Dynamic Current: 400 A max read
- Dynamic Current: 3mA max EEPROM write
- Battery Backup Current: <700nA @ 1.8V
• 100 kHz and 400 kHz Compatibility
• ESD Protection >4,000V
• More than 1 Million Erase/Write Cycles
• Packages include 8-Lead SOIC, TSSOP, 2x3
TDFN, MSOP
• Pb-Free and RoHS Compliant
• Temperature Ranges:
- Industrial (I): -40°C to +85°C.